head-to-head (Adjective) — Involving two persons; intimately private. ex. "a head-to-head conversation"
head-to-head (Adjective) — Inconclusive as to outcome; close or just even in a race or comparison or competition. ex. "as they approached the finish line they were head-to-head"
head-to-head (Adverb) — Even or close in a race or competition or comparison. ex. "the horses ran head-to-head"