v. 1 tr. a regulate or adjust. b moderate. 2 tr. adjust or vary the tone or pitch of (the speaking voice). 3 tr. alter the amplitude or frequency of (a wave) by a wave of a lower frequency to convey a signal. 4 intr. & tr. Mus. (often foll. by from, to) change or cause to change from one key to another. modulation n. modulator n.
[ L modulari modulat- to measure f. modus measure ]