Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pĕr-armo, āvi, ātum, 1, v. a., to arm or equip well (post-class.): perarmatus exercitus, Curt. 4, 9, 6; 23: manum gladius perarmat, Prud. Cath. 6, 85; 7, 93.