·adj Spiral; curved, like the spire of a univalve shell.
II. Helicoid ·adj Shaped like a snail shell; pertaining to the Helicidae, or Snail family.
III. 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.