Someone who doesn't go all the way down when doing reps on the bench or shoulder press so they can feel like they are stronger then they actually are.
This habit extends to all aspects of their life - they'll dominate a fat girl with zero sexual market value and think it makes them an alpha male, as an example.
The term "Half-Repper" was inspired by the song "Ain't No Half-Stepping" written by the legendary Big Daddy Kane in the late 1980s.
"Max is a total half-repper. He probably does half-reps in his girl's pussy as well."