a. [ Gr. &unr_;; &unr_;, &unr_;, spiral + &unr_; shape: cf. F. hélicoïde. See Helix. ] [ 1913 Webster ]

1. Spiral; curved, like the spire of a univalve shell. [ 1913 Webster ]

2. (Zool.) Shaped like a snail shell; pertaining to the Helicidae, or Snail family. [ 1913 Webster ]

Helicoid parabola (Math.), the parabolic spiral. [ 1913 Webster ]

n. (Geom.) 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. [ 1913 Webster ]

a. Same as Helicoid. -- Hel`i*coid"al*ly, adv. [1913 Webster]