Definition of number ones:
(adj) :
(idiomatic) First; foremost; best, often used after its headword.
(n) :
The most important person, the one who is in charge.
(n) :
Someone who is top of a ranking, who is ranked first.
(n) :
(music) The single that has sold the most in a given period.
(n) :
(soccer) The main goalkeeper of a team, so-called because they wear the number 1 on the back of their kit.
(n) :
Oneself, being considered foremost, as by an egoist.