Pronunciation: (ul'tru-sound"), [key]
1. Physics.sound with a frequency greater than 20,000 Hz, approximately the upper limit of human hearing.
2. Med.the application of ultrasonic waves to therapy or diagnostics, as in deep-heat treatment of a joint or imaging of internal structures. Cf. ultrasonography.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.