One-on-one means between just two people. A one-on-one meeting.
It changes what people will say, which is the entire reason for holding one. A one-on-one that is cancelled repeatedly says more than anything said in it would.
1adjectiveone-on-oneBetween just two people.
“The one-on-one lasted twenty minutes every fortnight for six years.”
one-on-one is a quality.