Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mūro, āvi, ātum, 1, v. a. [murus], to provide with walls (late Lat.): civitatem, Cassiod. Hist. Eccl. 12, 2; Veg. Mil. 1, 21: ca stella, id. ib. 3, 8: urbes, Hier. in Isa. 1, 2, 15 ext.