Someone caught in a state of paralyzing surprise, fear, or bewilderment. Likened to the tendency of deer to freeze in place in front of an oncoming vehicle. Often used in the phrase "like a deer in the headlights." Mary turned into a deer in the headlights when she forgot her lines in the middle of the play. He froze like a deer in the headlights when I caught him taking money out of the register. When she asked me to marry her, I could only stand there like a deer in the headlights.