(US, military) A communications unit and their equipment; most often in reference to satellite communications.

(group theory) A group that has a presentation without relators; equivalently, a free product of some number of copies of ℤ.

(mathematics) Any discrete group of isometries of the hyperbolic plane.

(organic chemistry) Any chemical entity that is temporarily reacted with a functional group so as to protect it from a subsequent reaction

scarce, or difficult to find.

An area of water used for fishing (usually a sea area).

(law, real estate) Rent paid under a ground lease, usually long-term or in perpetuity, for a surface right or estate in land where the landowner (surface owner) and the owner of improvements (ground lessor) are separate; the improvements are effectively security for the payment of the rent.

A group of cultivated orange trees

(chemistry) A functional group that is in close proximity to another that is taking part in a reaction; especially such a functional group that affects the rate or outcome of the reaction

(chemistry) An atom or group that is detached from the rest of a molecule during a reaction.