liberty cap

/L IH1 B ER0 T IY0 K AE1 P/
noun
  1. 1

    A brimless felt cap, such as the Phrygian cap or pileus, emblematic of a slave's manumission in the ancient world.

  2. 2

    A magic mushroom, Psilocybe semilanceata.

Source: https://en.wiktionary.org/wiki/liberty%20cap