from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Of or relating to acoustic frequencies above the range audible to the human ear, or above approximately 20,000 hertz.
- adj. Of, relating to, or involving ultrasound.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Beyond (higher in frequency than) the range of sound perceptible to the human ear; with a frequency of 20 kilohertz or higher.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. having frequencies above those of audible sound
ultra- + sonic (Wiktionary)