Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
trullĕum (trullĭum), i, n. [trulla], a basin, wash-basin, Varr. L. L. 5, 25, 34; id. ap. Non. 547, 6; Cato, R. R. 10, 2.
Called also trullĕus, i, m., Plin. 34, 2, 3, § 7; and trullĭo, ōnis, m., Plin. Val. 3, 38.