Meaning of old-man cactus

old'-man cac'tus

Pronunciation: (ōld'man"), [key]
  1. a Mexican cactus, Cephalocereus senilis, having a columnar body from 30 to 40 ft. (9 to 12 m) high with thatchlike, long, white hairs on the top, and red flowers with white centers.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.