(baseball) A base without a runner on it.

(chemistry) Any nucleophylic compound that can donate a pair of electrons and form a coordinate covalent bond.

(chemistry) Any compound, of general formula Xⁿ⁺, which can be transformed into a conjugate acid HX⁽ⁿ⁺¹⁾⁺ by the gain of a proton.

(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.

(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.

(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.

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

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