halfsome 

A surface of half cut of an object

The halfsome of a piece of the styrofoam looks like craters of a moon.

halfsome by Backdo January 26, 2019

one-and-a-halfsome 

Secks between a normal-sized person and a midget.

A twosome would involve two normal-sized people, so therefore a one-and-a-halfsome would involve a normal-sized person and a person half the size of a normal person, or a midget.

one-and-a-halfsome by Taco Monkey January 2, 2007

Two-and-a-half-some 

Sex involving a man, woman, and a midget of either sex.

Dude, I just had a two-and-a-half-some with Janice!

Two-and-a-half-some by Brett Y. Litsa August 18, 2010

Two and a Half-some

Two people are having sex. The third person is having oral sex performed on himself/herself by one of the people having sex.

Guy One: Yo, I totally took those two girls back home at the same time; it was awesome.
Guy two: You had a threesome?
Guy one: Not exactly. I only boned one of the chicks and ate the other one out at the same time. It was a Two and a Half-some.
Guy two: You are a legend!

Two and a Half-some by Dobs October 21, 2007

2 and a Half-some 

You and a friend discover someone passed out and take advantage of the opportunity before she wakes up.

Me and Jenny were going to find a nice spot on the beach all to ourselves, but we found a girl passed out in the sand. Best "2 and a Half-some" ever.

2 and a Half-some by PistachioPelicanFace July 5, 2010