When ones penis is no longer erect, possibly either after blowing ones load, or just losing an erection. A semi-boner is often used for playfully slapping ones friends in the face while they sleep for a hilariously good time.
by BLICK12 April 24, 2006
A semi-boner is when a man's penis is no longer erect after blowing his load or just becoming aroused.
by Tiea August 4, 2008
by tommysucks February 19, 2017
When your erection is only semi, it does not go all the way. This is actually more embaressing than a true boner because people think you 'cannot get it up'
HAHHAHAHA LOOK PHIL HAS A SEMI BONER OVER CHARLOTTE!
ITS PROBABLY OVER JOHNNY CAUSE ONLY HOMOS GET SEMI BONERS!
ITS PROBABLY OVER JOHNNY CAUSE ONLY HOMOS GET SEMI BONERS!
by chloerose444 August 14, 2008
by Cabbin February 13, 2018