numero uno

From either Spanish or Italian numero uno (“number one”).

numero uno (plural numero unos)

1. (informal) The most important of a group.

   Synonyms: see Thesaurus:important person

2. (informal) Oneself, especially one’s own interests.

   In his business ventures, he always looks after numero uno.

• look out for number one

numero uno m

1. the first in a series, or the most important in a group

• nemico pubblico numero uno