half mass 

The act of when a penis is half way erect, he slaps his penis across his partner's face.

when susan received a half mass from her husband, she was furious and bit off his nuts.

half mass by Jen Sing September 4, 2008

Half-Mass 

Half Boner; When the penis is not fully erect but still hard with a softness.

BROOO, I have the biggest Half-Mass

Half-Mass by Warfared November 28, 2012

half-mass 

when full bonerage has not yet taken place

Dude i was totally grindin with that babe over there at half-mass!

half-mass by jake January 17, 2005

Half-Massing It 

Comparative to the term Half-ass, although this is only used in church settings. A half Masser will leave Mass early because they feel that their time is too important to waste on staying the entire mass. The most common time to spot a Half-Masser is right before or during the final hymn of the mass, because they want to miss out on the massive cluster fuck that occurs in the parking lot immediate following Mass.
Half Massers are only above people who attend Mass once a year in terms of how much they are hated in the religious society.

...And God shed his ligggghhhht onnnn ussssss!!! ... Oh... Christ, there goes those Johnsons, I swear they are Half-Massing It every Sunday!

Half-Massing It by MrDomino December 28, 2007