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1.
a cooler way to state that something or rather some event is/was extremely bad.
"That was a crazy wipeout."
-"yeah, it was hainus, he tore himself a new asshole."
or
"my girlfriend dragged me out to see britany spears, the whole concert was hainus... but at least there were some hot chicks."
by Adam April 24, 2005
 
2.
An anus that is covered in a thicket of dirty hair.
Dude: Did you see how hairy his ass was when he bent over?

Other Dude: I closed my eyes, but it sounds heinous.

Dude: Yeah, a big ol' hainus.
by eplane April 12, 2012
 
3.
An adjective that describes how kickass something is. Something that is hot shit or even a hot cake can also be identified as hainus. People who are hainus are people who kickass.
-dude your mom is hot
-so, yours is hainus!
-oohh....
by Justin Merk January 20, 2004