number one

1 noun
Related topics: Music
number one1
1 [uncountable] the best, most important, or most successful person or thing in a group:
Until his marriage, his job was number one in his life.
Shearson is number one in the market this year.
2APM [uncountable and countable] the musical record that is the most popular at a particular time:
number one in the charts
They've had three number ones.

look out for number one

also look after number one spoken to look after yourself and not worry about other people, in a way that may seem selfish
4 [singular, uncountable] spoken informal a word meaning urine, used especially with children to avoid saying this

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