To engage in a desperate and almost equal contest.
1839. They are enemies, and let them lock horns. Of what age is that wondrous man you speak of?History of Virgil A. Stewart, p. 23 (N.Y.).
1888. The struggle in the convention came to be really a duel between Mr. Cleveland and the Boss of Tammany, with whom Mr. Cleveland had at an earlier period in his career locked horns.Bryce, American Commonwealth, ii. 562 note. (N.E.D.)