Definition of one-on-one adjective from the Oxford Advanced American Dictionary

 

one-on-one

 adjective
adjective
 
(also one-to-one)[usually before noun]
 
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between two people only Teachers do not have much time for one-to-one contact with their students. a one-on-one meeting
one-on-oneadverb
 
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He teaches one-on-one.
See the Oxford Advanced Learner's Dictionary entry: one-on-one