'Megaphone' definitions:

Definition of 'megaphone'

(from WordNet)
noun
A cone-shaped acoustic device held to the mouth to intensify and direct the human voice

Definition of 'Megaphone'

From: GCIDE
  • Megaphone \Meg"a*phone\, n. [Mega- + Gr. fwnh` voice.] A device to magnify sound, or direct it in a given direction in a greater volume, as a very large funnel used as an ear trumpet or as a speaking trumpet. [1913 Webster]