a cap of soft felt worn as a symbol of liberty, esp during the French Revolution, from the practice in ancient Rome of giving a freed slave such a cap
2.
a poisonous hallucinogenic basidiomycetous fungus, Psilocybe semilanceata, yellowish-brown with a distinctive pointed cap, found in groups in grassland
liberty cap in American English
a soft, closefitting cap without a visor, adopted by the French Revolutionists as a symbol of liberty