Merriam-Webster Collegiate Dictionary - amp

 I. noun  Etymology: by shortening  Date: 1886  1. ~ere  2. ~lifier; also a unit consisting of an electronic ~lifier and a loudspeaker  II. transitive verb  Date: 1972 excite, energize — often used with up trying to ~ up the crowd; also heighten, intensify — often used with up ~ up the drama AMP  noun  Etymology: adenosine monophosphate  Date: 1951 a nucleotide C10H12N5O3H2PO4 composed of adenosine and one phosphate group that is reversibly convertible to ADP and ATP in metabolic reactions — called also adenosine monophosphate, adenylic acid — compare cyclic ~