An attractive underage male. Similar to the female version, only not female. For similarities, see "Jailbait" or any of its other forms, but replace female with male, girl with boy/guy, chick with dude, her with him/he, etc.
Cougar-ette (Female in 20s) #1: Oh, wow! That guy is so hot. I want him.
Cougar-ette #2: Oh no way girl! He looks like he's 15 - that's totes malebait!