Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
tonstrīna, ae, f. [tondeo], a barber’s shop, Plaut. As. 2, 2, 76; id. Am. 4, 1, 5; id. Ep. 2, 2, 14; Plin. 36, 22, 47, § 165; 29, 6, 36, § 114; 35, 10, 37, § 112; cf. Becker, Gallus, 3, p. 136 (2d edit.).
tonstrīnum (-einum), i, n. [tondeo], the act or calling of a barber, Petr. 46; 64.