What is the meaning of Number_one?

First; foremost; best, often used after its headword.

Black, African-American.

The most important person, the one who is in charge.

Someone who is top of a ranking, who is ranked first.

Oneself, being considered foremost, as by an egoist.

Urine; urination.

The single that has sold the most in a given period.

The main goalkeeper of a team, so-called because they wear the number 1 on the back of their kit.

The batsman who opens the batting.

A first lieutenant.

A large town where theatrical performances may expect to achieve success.

Used other than figuratively or idiomatically: see number,‎ one.

Source: wiktionary.org