preamplifier Syllabification: (pre·am·pli·fi·er)Pronunciation: /prēˈampləˌfīər/Definition of preamplifier noun an electronic device that amplifies a very weak signal, for example from a microphone or pickup, and transmits it to a main amplifier. Derivatives preamplify verb (preamplifies, preamplifying, preamplified)preamplifier in other Oxford dictionaries Definition of preamplifier in the British & World English dictionary