one-on-one(s = adj.all)man-to-man - being a system of play in which an individual defensive player guards an individual offensive player; "one-on-one defense"
Adverbial has 1 sense
one-on-one(r = adv.all)person-to-person - (of two persons) in direct encounter; "interviewed her person-to-person"; "preferred to settle the matter one-on-one"