Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sŭb-ăro, no perf., ātum, 1, v. a., to plough close to any thing (Plinian), Plin. 16, 27, 50, § 116: subarata ocius senescunt, id. 16, 29, 51, § 119.