A loudhailer, also known as a megaphone, is a device that amplifies sound so that it can be heard from a distance. There are many synonyms for the word loudhailer, including bullhorn, loudspeaker, PA system, public address system, and sound system. These words are often used interchangeably, depending on the context and the specific device being used. Some other related terms include broadcasting equipment, sound reinforcement, and audio equipment. Whether you are looking to make an announcement, deliver a speech, or simply amplify your voice in a crowded area, a loudhailer can be a useful tool to have on hand.