Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
†† burgus, i, m. [cf. πύργος; Germ. Burg, Berg; Engl. -burg, borough, -bury], a castle, fort, fortress (post-class.): castellum parvulum, quem burgum vocant, Veg. Mil. 4, 10: crebra per limites habitacula constituta burgos vulgo vocant, Isid. Orig. 9, 2, 99; 9, 4, 28; Cod. Just. 1, 27, 2, § 4; Cod. Th. 12, 19, 2; Sid. Carm. 22.