Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
2. tersus, ūs, m. [tergeo], a wiping off, cleansing (Appuleian): lintea tersui profer, App. M. 1, p. 113, 2: tersui dentium petere aliquid, i.e. for tooth-powder, id. Mag. p. 277, 2.