You're browsing the GameFAQs Message Boards as a guest. Sign Up for free (or Log In if you already have an account) to be able to post messages, change how messages are displayed, and view media in posts.
You can interrupt a combo at just about any time by throwing a shiruken. Thus the term "shiruken cancel".
You can also string together combos by putting a shiruken cancel in and thus make "freeform" combos. I don't know any off hand but one might be X, Y, X, X, B, OL Y, B, X, Y, X, X.....etc.
This is a technique that is very useful and has been in just about all the current Ninja Gaiden games (Ninja Gaiden, Ninja Gaiden Black, Ninja Gaiden 2, Ninja Gaiden 3). I don't know if they had it in the NES games.