amplitude modulationn. Abbr. AM1. The encoding of a carrier wave by varying its amplitude in accordance with an input signal.2. A broadcast system that uses amplitude modulation.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.amplitude modulation n 1. (Telecommunications) one of the principal methods of transmitting audio, visual, or other types of information using radio waves, the relevant signal being superimposed onto a radio-frequency carrier wave. The frequency of the carrier wave remains unchanged but its amplitude is varied in accordance with the amplitude of the input signal. Abbreviation: AM or am Compare frequency modulation 2. (Telecommunications) a wave that has undergone this process Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014am (æm; unstressed ?m, m) v. 1st pers. sing. pres. indic. of be. [before 900; Old English am, eam, eom] AM 1. Asian male. 2. amplitude modulation: a method of impressing a signal on a radio carrier wave by varying its amplitude. 3. a system of broadcasting using this method. Compare FM. [1935?40] Am Chem. Symbol. americium. Am. 1. America. 2. American. A.M. Master of Arts. [