A person who attempted (or was accused of attempting) rape sometime during their highschool career. Whether they attempted the act or not, some drunk female may have accused them of such. In an SNL skit with Will Ferrell, he gives a shoutout to "hambone! check it out! tried to rape a girl in highschool!", and thus this definition.
<Alex> Hambone! Check it out! I heard you tried to rape that Becky chick!
<Harrison> Wow no. I definitely didn't try anything, stupid drunk girl.
<Alex> ...we're still calling you hambone forever now.