expression, ichidan verb
stare at; glare at; fasten one's eyes on
Colloquial expression, often with a nuance of glaring or staring intently at someone, sometimes with hostility or challenge.
See also: 眼をつける
あいつ、ずっとこっちをガンつけてるよ。
That guy has been staring at me the whole time.
ガンつけるなよ。
Don't glare at me.