short for superscript.
as in, sup.
sup is often accompanied by a flicking of the head in a superscript direction. if you know the person and made an assessment about their current happening (no need to talk), you can flick in the subscript direction (a quick nod).
sup means nihao and nihaoma, ohio gozaimas and mushimushi. are you cool? are you high (positive)? are you chill? are you good? i.e. how are you (rhetorical).
contraction of "what's up". something a duck might say while encountering a homie on the boardwalk. cooler than any other greeting simply because of it's brevity. three little letters that say so much. to say "sup" is to inquire, confirm, affirm and approve. it is a very comprehensive word.
"you know, just suppin' with my homies."
"that chonk is thicc af...imma go say sup."
"sup, Chip, what do you think about this new backpack?"
"suuuuup!!"