fog siren

fog siren

[′fäg ‚sī·rən]
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A siren used as a fog signal.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in classic literature ?
Each of the ladies, being after the fashion of their sex, highly trained in promoting men's talk without listening to it, could think--about the education of children, about the use of fog sirens in an opera--without betraying herself.