(1):

(n.) A kind of gallows; an upright post with an arm projecting from the top, on which, formerly, malefactors were hanged in chains, and their bodies allowed to remain asa warning.

(2):

(n.) The projecting arm of a crane, from which the load is suspended; the jib.

(3):

(v. t.) To hang and expose on a gibbet.

(4):

(v. t.) To expose to infamy; to blacken.