WordWeb Online

1. A reference to yourself or myself etc.; 'take care of number one' means to put your own interests first
    
2. The first or highest in an ordering or series
   "He wanted to be the number one"
   - first
    
3. The first element in a countable series
   "the number one of the month"
   - first, number 1

Derived forms: number ones

Type of: no., ordinal, ordinal number, rank, self

Encyclopedia: Number one