D defs.my
Entry 1 sense Webster, 1913

loony bin

/(lo͞on"y̆ bĭn)/ · IPA
01 n. An institution for the confinement or treatment of insane persons, such as an insane asylum or the psychiatric ward of a hospital.
  1. 1.
    An institution for the confinement or treatment of insane persons, such as an insane asylum or the psychiatric ward of a hospital.[slang]