Lewis & Short

extrēmĭtas, ātis (gen. plur. extremitatium, Plin. 29, 2, 9, § 32; cf. infra), f. [extremus], the extremity, end of a thing (class.): infinitas regiones, quarum nulla est ora, nulla extremitas, Cic. Fin. 2, 31, 102: mundus globosus est fabricatus, quod σφαιροειδὲς Graeci vocant: cujus omnis extremitas paribus in medio radiis attingitur, outer circumference, id. Univ. 6: circuli, Plin. 2, 17, 14, § 73; cf.: extremitatem et quasi libramentum (esse), in quo nulla omnino crassitudo sit (opp. punctum and lineamentum), superficies, Cic. Ac. 2, 36, 116: picturae, the outer edge, outline, Plin. 35, 10, 36, § 68.
In plur.: Aethiopiae, Plin. 6, 30, 35, § 188: lacuum, id. 31, 7, 39, § 73: corporis, id. 28, 6, 17, § 61; cf. absol.: febrium accessiones cum frigore extremitatum, the extremities, id. 23, 1, 24, § 48.
As rhet. t. t.: extremitates, extremes, extreme opposites, Quint. 11, 3, 15.
As gram. t. t., the termination, Prisc. ad Julian. Ep. §§ 5, 6.