halfsome
A surface of half cut of an object
The halfsome of a piece of the styrofoam looks like craters of a moon.
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.