bullhorn vs. megaphone

noun

  1. a directional, high-powered, electrical loudspeaker or megaphone.

noun

  1. a cone-shaped device for magnifying or directing the voice, chiefly used in addressing a large audience out of doors or in calling to someone at a distance.

verb (used with or without object)

megaphoned, megaphoning 
  1. to transmit or speak through or as if through a megaphone.