What is the meaning of Megaphone?

A portable, usually hand-held, funnel-shaped device that is used to amplify a person’s natural voice toward a targeted direction.

Mouthpiece or promoter; one who speaks for or publicizes on behalf of another.

To use a megaphone; to speak through a megaphone.

A cytotoxic neolignan obtained from the laurel Aniba megaphylla.

Source: wiktionary.org