number one - definition and synonyms

noun 

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singularnumber one
pluralnumber ones
  1. 1
    [singular] the person or thing that is first in order or importance

    The team is number one in the regional game.

  2. 2
    [countable] in popular music, the record that has sold the most copies in a particular week
  3. 3
    [singular] mainly spoken used for talking about yourself
    look out for number one (=protect your own needs and interests):

    You’ve got to look out for number one – no-one else will.

  4. 4
    [singular] urine. This word is used by children or when talking to children.
  5. 5
    [singular] a hairstyle for men that is slightly shorter than a number two