high sign

high sign idiom
A secret signal intended to warn or inform, as in Dad gave us the high sign when it was time to leave. This expression presumably alludes to a gesture such as a hand wave. [c. 1900]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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