First of all, most fighting games have either throw teching or throw softening, while Samurai Shodown has neither. Second, in Samurai Shodown if the opponent was not in a throwable state when the throw was input it results in a passive action (a hop) rather than a throw whiff. That generally makes throws quite valuable, especially since all normal throws have 3F startup and even auto-guard during the startup. However, there's quite a few ways to avoid being thrown in the first place. I'll go over the specifics of each one after this little quick-list:
- Ducking: 2D
- Hopping: 4D, 6D
- Throw-invulnerable move
- *Rolls: 1D, 3D
- *UOH: BC
- *Airborne Normal
But first, 5Sp has 17F throw invulnerability after blocking, being hit, or waking up off the ground (from being knocked down). That means during that time you have about a quarter of a second real-time before you become vulnerable to throws.
Most fighting games grant a period of throw-invulnerability status after hitstun, blockstun, and on wakeup: as seen here. But if you notice though, Samurai Shodown grants significantly more than any other game listed.
It also does not have any throw invulnerability off a reset. A reset meaning: knocked out of the air by a non-knockdown move. Such as being anti-aired or air-to-aired with a normal that hits you but places you back on your feet rather than knocking you down. This is important because both landing recovery and reset recovery are mostly identical, and therefor vulnerable to throws if left uncanceled.
Now for the explanations:
- Jumping. Jumps have zero startup animation. You transition from the ground to the air on the first frame of a jump. Therefor you are invulnerable to throws from the first frame of a jump input. However, not all jumps are created equal, some jumps are more floaty and more punishable than others, and they all have a cancelable landing recovery.
- Rejumps and Landing Recovery. This is important because while there is no jump startup, there is a cancelable recovery state on landing from a jump or from being reset. The amount of recovery time varies from character to character, however this can be canceled into any action including another jump. But, you can not simply hold up in order to cancel the recovery into a rejump. You must press the input once you have landed rather than before. If timed right this can avoid normal throws and even meaty command throws.
- Ducking. The 2D action has upperbody invulnerability (ducks under mids and highs) and is invulnerable to throws for 21F, starting instantly. After that window there is a special-cancelable window and a recovery window (4F and 7F respectively) where you can be thrown. This is generally the most ideal throw-bait, because your character is stationary during it. Thus, if the opponent attempts to throw during your laying-down state they will whiff a grab instead of a hop, which has a rather long punishable whiff animation. Other anti-throws (hops/jumps/etc) usually cause the opponent to whiff a hop (6D) instead of whiffing a throw, but 2D has a large throw invulnerability period that can bait out an actual throw whiff.
- Hopping. The 4D and 6D movements have lower body invulnerability (dodge lows), are instantly throw invulnerable, and remain throw-invulnerable until landing. They are also special-cancelable on landing. This is less ideal than the 2D action for baiting throws because you are instantly airborne during these hops, which means if the opponent attempts a throw after you've left the ground they will not whiff a grab, instead they will whiff their own hop (either 4D or 6D). They will only whiff a grab if you were on the ground when they input it, but you hopped during their 3F throw startup window. However, this action is still valuable in the sense that hops avoid lows (but vulnerable to mids/highs), while the 2D action is vulnerable to lows (but avoids mids/highs).
- Backdash. The 44 action is bufferable and instantly throw invulnerable. It also has about 3F of full-body invulnerability on startup. It is also air-special cancelable while airborn and ground-special cancelable on landing. However, it should be noted that despite being bufferable there is always a 1-2F suki on landing from a jump or reset before a backdash will begin. This is unique only to backdashes and only on landing from a jump or reset. It also means that backdashes when buffered correctly will always avoid normal throws, but they can be grabbed by meaty command throws due to the backdash suki. Backdashes are quite valuable for avoiding normals throws in general due to the prebuffer window. But it suffers the same issue as hops in the sense that it won't bait out a throw whiff as well as a duck (2D).
- Throw-invulnerable moves. Some special moves gain the property of being throw-invulnerable. This is entirely character specific and may or may not have anything to do with other forms of invulnerability or ground/air-state. A good example would be Yoshitora's 236B (Mid-Nadeshiko) which is not hit/projectile invulnerable or airborn, but it is throw invulnerable on startup. Likewise Yoshitora's 623AB (Heavy-Shirayuri) is hit-invulnerable on startup but not throw invulnerable.
- Rolls. The 1D and 3D actions are 3F full invulnerability on startup. During this time they can avoid throws by virtue of total-invincibility. However, the forward roll is quite vulnerable to throws any time after the startup invulnerability wears off. On the other hand, the backwards roll is slightly better at avoiding throws by virtue of it moving away from the opponent, potentially outside of throw range. Still, forward rolls are probably the least ideal method of avoiding throws while backwards rolls are decent due to the early special-cancel-ability.
- UOH. The B+C action is usually airborne after the third frame, except for some characters like Haohmaru/Charlotte/Gaira/etc. Though, if your character does leave the ground within 3F then it can be useful for avoiding throws in some situations while still granting the potential of hitting the opponent as a nice option select.
- Airborne Normal. There are character specific moves that become airborne rather quickly. For example, 5C for Amakusa, Sogetsu, Suija, etc. They are usually not throw invulnerable on the first few frames, but after the startup occurs they have the same benefit of UOH's in that they become airborne and attack at the same time.
Mina is special in that her jumping arrow attacks incur a 7F uncancelable recovery on landing. This is a true-uncancelable period for Mina's air arrows, however she can block during this uncancelable time (EG. she can perform no action other than blocking). This only effects her air arrows, not her jumping kicks or unarmed attacks or empty jumps.
Bottom line (tl;dr version):
2D is your best bet for baiting throws. Perfectly timed rejumps is your best bet for avoiding meaty command grabs on landing. Backdashes are bufferable and therefor your best bet for avoiding normal throws in most situations (but not for avoiding meaty command throws). To avoid getting hit out of anti-throws it's important to vary what you do, for example ducks and hops have upperbody and lowerbody invulnerability respectively.
On landing: Backdashing always has a 1-2F suki on landing, regardless of anything. The D actions and anything other action have a 0-1F suki randomly. Rejumps never have any suki period.