derail(redirected from derailing)
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Chiefly US a device designed to make rolling stock or locomotives leave the rails to avoid a collision or accident
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
To cause a railroad car or engine to run off the rails.
A device to guide railway cars or engines off the tracks to avoid collision or other accident.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.