zagryzać

Etymology
From.

Verb

 * 1)  to bite to death
 * 2)  to drive someone to extreme exhaustion by tormenting
 * 3)  to chase, to wash down
 * 4)  to bite each other to death
 * 5)  to drive each other to extreme exhaustion by tormenting
 * 6)  to drive oneself to extreme exhaustion or depression by worrying about something