Expressions (phrases, clauses, etc.), Godan verb with 'mu' ending
to regret bitterly; to be very sorry (for); to bite one's navel
Idiomatic expression
彼女は姑の気にさわるようなことを言わなければよかったと臍を噛んだ。She bitterly regretted having said something that displeased her mother-in-law.
Also written ほぞを噛む【ほぞをかむ】、臍を噬む【ほぞをかむ】