brucho describes the hostile action of gnashing teeth at someone.

The attested use describes a plural group gnashing their teeth at someone in a hostile response after hearing what was said.

1. Gnashing teeth in hostility · dominant

   In Acts 7:54, ἔβρυχον is a third-person plural imperfect active indicative form describing the response of those who heard these things; the APB renders the clause “and gnashed their teeth at him.”

   Acts 7:54

In the Anselm Project Bible: In Acts 7:54, the APB presents the action as “gnashed their teeth at him.” This rendering confirms the clause's overall hostile response rather than isolating every feature of the Greek form.