A potential partner that isn't attractive and requires at least a six pack to have intercourse with.
John hooked up with a sixer upper last night... She looked like a yeti.
by Hellz1117 August 23, 2008
Derived from "Fixer Upper". A potential mate that typically falls below standards of attraction, but with a 6 pack is attractive.
"She's alright, but that mole on the face makes her a sixer upper"
by Hellz1117 July 15, 2008