definition of
number one

[1] #1 number one n. a reference to yourself or myself etc.; 'take care of number one' means to put your own interests first. wn

[2] #2 number one n. the first or highest in an ordering or series; "He wanted to be the first". wn

[3] #3 number one n. the first element in a countable series; "the first of the month". wn