Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
plostellum, i, n. dim. [plostrum, plaustrum], a small wagon or cart: plostellum Poenicum, Varr. R. R. 1, 52: plostello adjungere mures, Hor. S. 2, 3, 247; Aug. Civ. Dei, 7, 21.