Green’s Dictionary of Slang

(US) to stare aggressively.

1986		R. Campbell In La-La Land We Trust (1999) 41: They were hard-eying each other. Tillman had money and was actor-trained, so he was better at it.
2008		G. Pelecanos Way Home (2009) 15: Jason stopped and hard-eyed the kid.
2011		J. Scott StoneDust 188: The dozen beer drinkers hard-eyeing me back saw a guy dumped by his girl.