Real Dictionary

Senor
You use Senor when you are speaking to or referring to a Spanish-speaking man.

señor in American English
Mr.; Sir
noun: a Spanish term of address equivalent to sir or Mr., used alone or capitalized and prefixed to the name of a man

senor in British English
noun: a Spaniard or Spanish-speaking man: a title of address equivalent to Mr when placed before a name or sir when used alone
noun: Spanish term of address equivalent to sir or Mr