A kind of seaweed whose bladders may be used by children as whistles.

plural of whistle board

(railways) A sign marking a location where a locomotive engineer is required to sound the horn or whistle.

plural of whistle post

(railways) Synonym of whistle post

plural of peanut whistle

(CB radio, slang) A low-powered transmitter or receiver.

(music, historical) An Aztec instrument, sometimes shaped like a skull, that when blown produces a human-like shriek.

plural of death whistle

(simile)