Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sŭb-ostendo, di, sum, 3, v. a., to point out secretly, to show indirectly (post-class.): aliquid, Tert. adv. Marc. 4, 38 med.; id. adv. Valent. 1: spes adventus Domini subostensa, id. Bapt. 19; id. Anim. 12.