I am trying to settle an argument here. Based on the old bible thing about the earth being a circle. Other poster contends that a square is three dimensional, and so is a triangle. I want to retort that a 3d square is called a cube, but want to see if there is a name for a 3d triangle. Any idea?

Tetrahedron.

It has 4 sides all triangular (3 sides and bottom)

A 3D circle is a sphere, by the way.

A solid, 3D triangle is a pyramid.

A solid, 3D triangle is a pyramid.

A pyramid is 4 triangular sides and a square base.

Guess the OP didn't clarify which he was looking for.

A 3D circle is a sphere, btw.

I told him that, and he claims, that there the circle is NOT a sphere. I hate ignorant people.

I told him that, and he claims, that there the circle is NOT a sphere. I hate ignorant people.
A circle is flat, two-dimensional. A sphere is a ball, three-dimensional. He can Google it if he doesn't believe you.