The MTG Urban Dictionary - Ape (n., v.)
Ape (n.)
1. A player who makes terribad plays.
Sam: Chris had his opponent dead on board but didn't attack.
Cherry: No surprise. Chris always plays like an ape.
Ape (v.)
1. To play poorly.
Melissa: Good luck at the Grand Prix tomorrow!
Scott: Thanks! Hopefully I won't ape it up on camera.
Additional Reading
1. Financial Quick Picks - MTG Hit List, Get in before Pro Tour Oath of the Gatewatch [Edward Eng]
2. The MTG Community - 2015 Yearly Review [Edward Eng]