to bite one's tongue
Tive que morder a língua para não falar o que eu realmente pensava do chefe.
I had to bite my tongue to not say what I really thought about the boss.
The image is bodily and immediate: to clamp your teeth on your own tongue is to stop it moving and silence the words it was about to form. Morder a língua thus means to hold back something you were on the verge of saying — or, after the fact, to wish you could take it back.
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