look up any word, like smh:
 
2.
when you see a hot girl and you dont have time to think and you penis is up
omg that girls tight ass gave me an instant boner

look at the instant bonerfying cleavage over there

i have a boner right now just so you know
by ieatmonkeybutt69 February 28, 2011
 
1.
when u c a broad so sexc that ur dick juss pops up
oh shit check out that broad man instant boner
by mikeiliketoridedykes September 05, 2006