n The digit or figure 1.
n (by ellipsis) Used to briefly refer to a noun phrase understood by context
n (US) A one-dollar bill.
n One o'clock, either a.m. or p.m.
n (cricket) One run scored by hitting the ball and running between the wickets; a single.
n A joke or amusing anecdote.
n (followed by for) A person (having some specified characteristic or attribute).
n (colloquial) A particularly special or compatible person or thing.
n (dated, euphemistic or derogatory) A gay person.
n (mathematics) The identity element with respect to multiplication in a ring.
adj Of a period of time, being particular.
adj Being a single, unspecified thing; a; any.
adj Sole, only.
adj Whole, entire.
adj In agreement.
adj The same.
v To cause to become one; to gather into a single whole; to unite.
n (Internet slang, leetspeak, sarcastic) Deliberate misspelling of !. Used to amplify an exclamation, parodying unskilled typists who forget to press the shift key while typing exclamation points, thus typing "1".