| a gesture, glance, or facial expression used as a surreptitious signal to warn, admonish, or inform. |

| high sign n. Informal A prearranged signal intended to warn or inform: gave me the high sign that it was time to leave. |
high sign
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high sign
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]