Meaning of liberty cap

lib'erty cap"

Pronunciation: [key]
  1. a soft, conical cap given to a freed slave in ancient Rome at manumission of his servitude, used as a symbol of liberty, esp. since the 18th century. Cf. Phrygian cap.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.