Overmatch, v. t.
1. To be more than equal to or a match for; hence, to vanquish. Drayton.
2. To marry (one) to a superior. [Obs.] Burton.
1 other Webster entry under this spelling
Overmatch, n.
One superior in power; also, an unequal match; a contest in which one of the opponents is overmatched. Milton. D. Webster.
Shades of meaning
Fernald has no entry of its own for overmatch; he lists it under conquer.
He lists it without comment; the entries above explain its neighbors.