Definition of "eyeball"

Goe make thy ſelfe like a Nymph o' th' Sea.Be ſubiect to no ſight but thine, and mine: inuisibleTo euery eye-ball elſe: goe take this ſhape,And hither come in't: goe: henceWith diligence.

1610–1611 (date written), William Shakespeare, “The Tempest”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene ii], page 4, column 2

Intelligence work is necessarily limited in scope by the capacity of national surveillance systems. […] Ultimately, it is only when you have an 'eyeball' or the electronic equivalent on a suspect that you have a reasonable chance of a preventive intervention.

2016, Marie Breen-Smyth, The Ashgate Research Companion to Political Violence, page 384

When The Lord of the Rings: The Rings of Power debuted at the same time as House of the Dragon, much noise was made about which show attracted more eyeballs.

2022 October 17, Stuart Heritage, “Now it’s over, let’s come out and say it: The Rings of Power was a stinker”, in The Guardian‎

Guardiola strode on to the pitch at half-time to remonstrate with the Spanish referee, Antonio Mateu Lahoz, but went too far with his eyeballing and matador-like hand movements. He was “upstairs”, in the Colin Bell stand, to watch Liverpool’s second-half turnaround and a dismal seven days for City take another turn for the worse.

2018 April 10, Daniel Taylor, “Liverpool go through after Mohamed Salah stops Manchester City fightback”, in The Guardian (London)‎