From Longman Dictionary of Contemporary Englishone-to-oneˌone-to-ˈone adjective 1 TWObetween only two people tuition on a one-to-one basis2 SAMEmatching each other exactly a one-to-one correspondence between letters and sounds —one-to-one adverb I need to discuss it with him one-to-one.
Examples from the Corpus
one-to-one• one-to-one counseling• There was a rally in the euro, but hopes of a recovery to a one-to-one parity did not materialise.• He preferred to keep his friends separate: a one-to-one person.• It will soon be as good or better than one-to-one teaching, say enthusiasts. 