out (of) the corner of (one's) eye
Of something seen, in one's periphery; partially and/or fleetingly, as opposed to fully and for an extended amount of time. Out the corner of my eye, I saw something moving in the bushes, and it turned out to be a stray cat. Sarah caught Tommy kissing Jessica out of the corner of her eye.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.