side + eye.
side-eye (countable and uncountable, plural side-eyes)
- A sidelong look of animosity or suspicion.
2018 May 20, Hadley Freeman, “Is Meghan Markle the American the royals have needed all along?”, in Katharine Viner, editor, The Guardian, London: Guardian News & Media, ISSN 0261-3077, OCLC 229952407, archived from the original on 21 October 2018: I saw some snarking online about Bishop Michael Curry's passionate sermon, and certainly the royal family seemed unnerved by it, with Zara Philips watching it in apparent open-mouthed shock and Kate and Camilla shooting each other some heavy side-eye.
sidelong look of animosity or suspicion
side-eye (third-person singular simple present side-eyes, present participle side-eyeing or side-eying, simple past and past participle side-eyed)
- (transitive) To look at out of the corner of one's eye.
to look at out of the corner of one's eye