set (one's/someone's) back up(redirected from sets their backs up)
set (one's/someone's) back up
To be or become angry, hostile, defensive, or irritable, or to cause such a feeling in someone else. John started setting his back up when his parents brought up the subject of college again. Election season always sets my dad's back up. Few things set my back up like hearing about a poacher killing an endangered animal.