adj spiral; curved, like the spire of a univalve shell.
2. helicoid ·adj shaped like a snail shell; pertaining to the helicidae, or snail family.
3. helicoid ·noun a warped surface which may be generated by a straight line moving in such a manner that every point of the line shall have a uniform motion in the direction of another fixed straight line, and at the same time a uniform angular motion about it.