amplifier

Short definition from Wiktionary

Noun

1. 1
   Anything that amplifies, or makes something larger or more intense.
2. 2
   An adverb that adds intensity, such as "really" or "totally".
3. 3
   An appliance or circuit that increases the strength of a weak electrical signal without changing the other characteristics of the signal.
4. 4
   A portable encasement that houses a large speaker, used to amplify voices and musical instruments at live performances.
5. 5
   A lens that enlarges the field of vision.