n. A train with two engines, (predates baseball term).
n. Two games played on the same day at the same venue.
n. Two fishermen each catching a fish at the same time.
the GNU version of the Collaborative International Dictionary of English
n. two events, usually entertainment or sports performances, occurring immediately in succession or within a short time of each other; especially, two sports games played by the same teams on the same day, one right after another.
The Century Dictionary and Cyclopedia
n. A railroad-train drawn by two engines, or pulled by one engine and pushed by another.
n. In lumbering, a place from which it is possible to haul a full load to the landing, and where partial loads are topped out or finished to the full hauling capacity of teams.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. two games instead of one (especially in baseball when the same two teams play two games on the same day)
Word Usage
""Winning a doubleheader is a very difficult thing to do in the big leagues," Rangers manager Buck Showalter said."