A word used to make fun and or annoy someone, such as Jeffrey, if you are pissed that they are beating you in COD. A ploomer is a dimwitted or annoying person, or someone who is generally getting on your nerves for whatever reason.
Guy 1: Ohhh take that! I just got a care package in cod!!
Guy 2: Wow... your such a PLOOMER!
Guy 1: *Knocks on door*.
Guy 2: *Opens door*
Guy 1: Hey, PLOOOMER!