gnash one's teeth, to

gnash one's teeth

Fig. to grind or bite noisily with one's teeth. Bill clenched his fists and gnashed his teeth in anger. The wolf gnashed its teeth and chased after the deer.
See also: gnash, teeth
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

gnash one's teeth

Express a strong emotion, usually rage, as in When Jonah found out he was not going to be promoted, he gnashed his teeth. This expression is actually redundant, since gnash means "to strike the teeth together." Edmund Spenser used it in The Faerie Queene (1590): "And both did gnash their teeth." [Late 1500s]
See also: gnash, teeth
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.

gnash one's teeth, to

To express one’s anger or frustration. This term, dating from the late sixteenth century, is redundant, since to gnash means “to strike the teeth together.” Today the verb is practically always figurative (no one actually strikes the teeth together) and is never heard except in this cliché. The King James Bible of 1611 has it: “But the children of the kingdom shall be cast out into outer darkness; there shall be weeping and gnashing of teeth” (Matthew 8:12).
See also: gnash
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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