bite down

verb3

1. •
   To bite (something) very hard and usually for a purpose (like to hold it in one's mouth).

   • Biting down on my wallet, I had two hands free to open the door.
2. •
   To clench with one's teeth.

   • He bit down to force himself not to say anything.
3. •
   (figurative) To repress or bite back an (emotion, impulse or reaction).

   • She bit down on the urge to strike the woman who had wronged her.