Definition
A music-driven subculture and slang label for someone marked by intense emotional expression, moody or melancholic themes, and a dark, angsty fashion/aesthetic.
Examples
"He went through an emo phase, with black nail polish, fringe bangs, and heartbreak lyrics scribbled in his notebook."
"That track is so emo, all raw confessionals over chiming guitars and a brooding, melancholic vibe."
"The new kid is pretty emo—quiet in class, heavy into basement shows, and always in a black hoodie."