1 [mass noun] the undesirable effect in flash photography of people appearing to have red eyes, caused by a reflection from the retina when the flashgun is too near the camera lens:a pre-flash emission to minimize red-eye
(also red-eye flight) [in singular] informal, chiefly North American a flight on which a passenger cannot expect to get much sleep on account of the time of departure or arrival:she caught the red-eye back to New York
2a freshwater fish with red eyes, in particular:
British a rudd.
North American a rock bass.
3 [mass noun]US informal cheap whisky.
Canadian a drink made from tomato juice and beer.
red-eye in other Oxford dictionaries
Definition of red-eye in the US English dictionary