gay panic

Gay panic has two distinct meanings.

In law, it's a defense strategy claiming a defendant was provoked into violence by an unwanted same-sex advance—He argued gay panic after killing the man who propositioned him.

In casual usage, gay panic describes the anxious, flustered reaction of someone confronting their own same-sex attraction or an unexpectedly homoerotic situation: She's in full gay panic mode around her new coworker.