The Greek verb brychō (βρύχω) means to gnash or grind the teeth, specifically with rage or anguish. It appears only once in the New Testament (Acts 7:54), describing the reaction of the Sanhedrin to Stephen's speech: "they were furious and gnashed their teeth at him." The word captures a visceral, animalistic expression of uncontrolled rage.
The gnashing of teeth in Stephen's martyrdom (Acts 7:54) mirrors Jesus's descriptions of the final judgment, where "there will be weeping and gnashing (brygmos) of teeth" (Matthew 8:12; 13:42, 50; 22:13; 24:51; 25:30; Luke 13:28). The Sanhedrin's physical response to Stephen's proclamation of Christ gives us a preview of eschatological rejection: the same rage that covered their ears and rushed upon Stephen (Acts 7:57) is the rage of those who refuse to bow before the exalted Lord Jesus. Stephen's response — "I see the Son of Man standing at the right hand of God" — is the unbearable truth that provoked their gnashing.