gnash your teeth
gnash (your) teeth
to show you are angry or annoyed about something bad that you cannot do anything to stop.
His advisers are gnashing their teeth in frustration because he refuses to attack his opponent on foreign policy issues.
Usage notes: also used in the form gnashing of teeth:
The first test-tube baby was born in 1978, to considerable gnashing of teeth.
Because we do not have a HW "gnashing," it makes sense to include it here under the verb, even tho it is slightly more common; there is often a slightly humorous tone to this use, but not enough, I think, to label--SL, 2/03