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1.
A male, usually geeky, Who when offered the chance to have sex, stands up and walks away awkwardly shouting BYEE, leaving their partner naked and confused.
"Alright steve, take off your glasses and fuck me"
"UHHH OH GOD -inhaler- i got to go BYEEE"
"uhh like WTF STEVE?! Your a goddamn Bye-Sexual!"
by Soljaboisafaggot November 25, 2009
 
2.
Defines a type of person whom you might really be into, but is only interested in you long enough to have sex with you, and drops out of your life immediately after, looking for the next bang. Can be used to describe dudes or chicks.
Jack: "Last night was amazing. How about your number so we can do this again sometime?"

Sally: "Sorry...I'm what you call a "BYEsexual". Once I have sex with you...BYE!!!"
by CactusHeart May 05, 2011