(baseball) To touch a base, usually with a foot but sometimes with a hand.

(baseball) A base without a runner on it.

(baseball) The base after second base in a counter-clockwise path around a baseball infield. / (blackjack) The betting spot located immediately to the right of the dealer, which is last to act.

(singular only, baseball) The base after home plate in a counter-clockwise path around a baseball infield. / (singular only, by extension) Completion of the first phase of an activity.

(baseball) The base opposite home plate in a baseball infield. / (singular only, US, colloquial) Touching a partner under his or her clothes, without having sex.

(obsolete, 1800s) baseball

(military) A military airport, providing housing and support for aircraft and personnel.

(chemistry) An imine.

(telecommunications, military, US) Communications services, such as the installation, operation, maintenance, augmentation, modification, and rehabilitation of communications networks, systems, facilities, and equipment, including off-post extensions, provided for the operation of a military post, camp, installation, station, or activity.

(chemistry) any molecular entity capable of accepting a proton from an acid