eyeball
noun
[ ˈʌɪbɔːl ]
• the round part of the eye of a vertebrate, within the eyelids and socket.
eyeball
verb
• look or stare at closely.
• "we eyeballed one another"
eyeball to eyeball
• face to face with someone, especially in an aggressive way.
• "he wheeled round to confront John eyeball to eyeball"