intransitive. To cower or tremble with fear; to back out of something; to surrender in a cowardly fashion. Also with at.

intransitive. To behave in a cowardly manner.

With on: to betray or let down (someone). Also without const., to funk, to behave in a cowardly manner; to wriggle or squirm. Australian slang.

intransitive. slang (originally and chiefly U.S.) to pussy out: to back down, back out; to act like a coward. Cf. wimp, v.

intransitive. Ugandan English. To act like a coward; to lose one's nerve or resolve, to ‘chicken out’.