An affirmation, usually positive and resolute, indicating a more legimate, committed response than the conventional, vernacular "yes."
It may be used in any place in the standard English sentence as often and frequently as possible.
While its origin has yet to be definitively confirmed, the term is widely believed to have originated sometime in the early 21st century in the Columbia region of the Island of Manhattan, when used by the feminist historian and future president popularly known as Annie T. Since her incorporation of the term into the common English of Ivy League academics, 'forsure' has become an international phenomenon. It is estimated that "forsure" is spoken 2309402589247646 times per minute internationally, and 2390402580582 times per second between 110th and 116th streets.
KC: "Are you up for some 'ruit tonight?"
AT: "Oh for sure dude. Plus the Sox/Yanks are on which we for sure have to see."
KC: "Oh totally, the sox are for sure taking this series and what's better than beirut and the sox?"
AT: "ruit, sox and ganj dude"
KC: "for sure"