One-to-one (communication)
WordNet
adjective
(1) Used of relations such that each member of one set is associated with one member of a second set
WiktionaryText
Noun
one-to-one
- A personal relationship, especially a sexual one, between two people. Colloquial abbreviation: 121 or 1-2-1
- injection; a mapping which takes no two points in the preimage to the same point in the image