Half-On 

A semi-erect penis. (See: Semi, Chub) Fifty percent of a Hard-On. A "bulge in the pants," as it were.

I often get a half-on while leering at females on the subway.

Half-On by Time4SumAksion September 22, 2005

Half-on 

When a mans dick gets bigger but not hard enough yet to not be bendable either with starting to get a boner or starting to go down.

Damn that guy has a huge dick

Nah he just has a half-on

Half-on by Its_Fucking_T0m June 14, 2011

half on

Like a hard on, it comes about when some thing is arousing, but not enough to induce a full erection.

While watching two average women make out, Jim noticed that he was sporting a half on.

half on by Harry T August 17, 2007

half on a sack 

Splitting half the money for a bag of weed.

Yo, you tryin' go half on a sack?

half on a sack by Nignoggins November 17, 2015

half on a baby 

To share a baby with a lover/partner pretty much saying you’ll both take care of the baby equally

Damn I really love her. With her, I would go half on a baby.

half on a baby by Almightty_L January 11, 2018

Half on a bud sack 

Throwing half the money towards a bud sack when cheifing with one of your homy's.

Killam: Wuzz up my nigga, half on a bud sack.

Nick: How much you wanna get.

Killam: Wanna cop a zone.

Nick: Hell yeah.

Killam: I'll hit up tha d-man and go get some Swisha's.

Half on a bud sack by Killam Willam December 14, 2008

Halfon [half on]

Half of an erection.

Not quite full wood, but kind of there.

"Halfon half on is her last name, like a limp dick?"

Halfon [half on] by Austin Walker December 31, 2008