Mastercheifing 

Verb-
A. Mastebating while playing halo (1, 2 , or 3, because wars sux).
B. owning at halo.
C. being epic in any way, shape or form.

in-game kid: Hay Guyz im mastercheifing it up in my pants!
other kid: GROSS!

OMG i am SOOO mastercheifing *killionare*

im soooo mastercheifing *<<< chuck norris talking, of coarse*

Mastercheifing by the cheifer November 27, 2010

masturchiefing 

The act of pleasuring one's self with the intention of sexual gratification while playing the Halo series.

Halo Fanboy #1: "Hey, wanna troll on a Playstation website?"

Halo Fanboy #2: "Wait! I'm not done masturchiefing yet!"

masturchiefing by D4ng3rM4n January 5, 2012

Masterchiefing 

Verb; When one breaks up his or her weed on the case of any game in the Halo series. i.e. Halo, Halo 2, Halo 3, etc.

DOOOOOOODE, we totally broke up some DANK ASS SHIT on Halo 3 last night and we were Masterchiefing the fuck out of it!

Masterchiefing by BITTERwork May 14, 2011