The term “sukashi” in Japanese fighting game terms, is a ren'yōkei form of the verb “sukasu” (in this case, used as a gerund). The verb means different things in different contexts; referencing WWWJDIC:
As one could guess, even without knowing the Japanese language, while these are different words with the same pronunciation, the connotation is pretty much the same: something is missing or gone, and perhaps on purpose.
While sukashi on its own would thus mean to miss something in order to be deceptive (e.g., deliberate zoning), it almost always refers to an “empty” jump – a jump where one forgoes any action possible during the jump.
A typical jump attack has an overhead hitbox, so it has to be blocked standing. However, if the jumper does not use a jump attack, it is unlikely that the defender can use a standing block to defend, making the empty jump a good pathway to option pressing.
The below methods are uses of the empty jump, but keep in mind that either player can mess up the setup by attacking.
An extremely simple way to utilize an empty jump is to perform a throw with a landing cancel right after landing. If this throw is a 1-frame throw, it will be impossible to defend against without some modicum of reading ahead.
The advantages to this approach are that it can only be avoided by jumping or intercepting with an attack.
Throws have a set amount of damage, and normal throws (which all characters can use) are unreliable for decent damage in most games. For those reasons, you should also consider using a low-hitting move (especially one from which you can start a combo) to increase your returns.
The weakness here is that it can be defeated in the same ways as the throw (jump or interception), as well as by a simple switch to a crouching block.
A special instance of option pressing while jumping in – let’s say that you know a jump will be safe (e.g., the opponent is knocked down, and you know they will get up some time later). In some games (especially old-school games like Street Fighter II), if instead of a risky meaty crossup attempt, you time the jump just so, you know that no matter what the opponent does, they will either break even or lose when you attempt an attack.
If they block, they only block a hit. If they attempt anti-air on wakeup, you will land in time and block.
The advantage to this form of empty jump is that your timing does not need to be exactingly perfect, only good (and in fact, many players happen upon this strategy without ever giving it much thought).