Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ŏnusto, āre, 1, v. a. [onustus], to burden, load (only late Lat. and in Part. pass.): virgo reguli partu onustanda, Aug. Serm. 3 in Nat. Dom. 2. Verg.: nomen sollicitudinibus onustatum, Cassiod. H. E. 10, 33; Vulg. Judith, 15, 7.