1) exclamation regarding something that should not have been possible to do.
2) exclamation concerning or referring to something which is impossibly astounding and/or astoundingly impossible.
Did you see the size of that guys smegma? Un-Fucking-Believable.
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).
Precedes or follows either a gratuitously disrespectful or honest remark, originated in New York City. Used in similar fashion to "no offense" or "to be honest," interchangeably.
Ya mans is wild buns, respectfully. Respectfully he's washed.
After school, The Modells on Jamaica Ave was active. Respectfully.