Adj. The condition in which you forget who, where, and how you fucked. (Most common in drunk ass fucks.)
"We fucked before??? damn, I must have fucknesia." or "I must have fucknesia cause I don't remember nutting on your ear???"
by I forgot...Fucknesia! June 13, 2004
Girl: We need to have sex. It's been a while.
Boy: What?!? We just had sex last night!
Girl: Damn, I must have fucknesia!
Boy: What?!? We just had sex last night!
Girl: Damn, I must have fucknesia!
by NymphoCRS May 4, 2011