When it is so hot you back is coated in sweat, like after sex.
Walking around in this heat has totally given me sex-back.
by Daniel Ka June 21, 2007
A flashback to sex - often after a particularly drunken night. Can be triggered by anything from a particular smell to a rude pain.
Joy stopped mid-conversation as she had a Sexback to the night before, when she remembered shagging a tramp down the back of the church.
by LeWoolfe May 20, 2010