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2.
Stands for "Huge In All Formats". This acronym is used when a professional athlete makes a big play that would help owners of that player in fantasy leagues. The opposite of HIAF is DIAF which stands for Droppable in All Formats.
Announcer: Albert Pujols had 3 home runs, 5 hits, and 4 runs!
Fantasy Analyst: HIAF!

Lebron James: Just look at my stats bro.
Fan: HIAF! Keeper status!
by *xpac taunt* October 28, 2011
 
1.
High as fuck.

May be pronounced "Hee-yaff" for purposes of concealment when among unfavorable parties.
Bro I was hiaf last night after hittin' Derek's bong.
by JeromesNiece July 01, 2013