number one

.number 'one¹ n

1.) [U]

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.

2.) [U and C]

the musical record that is the most popular at a particular time

▪ number one in the charts

▪ They've had three number ones.

3.) 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, U] spoken informal a word meaning ↑urine, used especially with children to avoid saying this directly

number one ²

.number 'one² adj

1.) most important or successful in a particular situation

▪ The University of Maine has the number one hockey team in the country.

▪ Sweden's number one model

2.) first on a list of several things to be considered, done etc

▪ item number one on the agenda

▪ This has got to be our number one task.