1
general::
Exactly, precisely; especially, at the appointed time or estimated amount. For example, The busload of students arrived at the museum at ten o'clock right on the nose, or He guessed the final score on the nose. This term, like ON THE BUTTON, may come from boxing, where the opponent's nose is a highly desired target. [c. 1930]
American Heritage Idioms
2
general::
Phrase(s): on the nose
Go to on the money.
McGrawhill's American Idioms And Phrasal Verbs