Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
serrŭla, ae, f. dim. [serra], a small saw: dentata, Cic. Clu. 64, 180: ferrea, Varr. R. R. 1, 50, 2: aliquid ossis serrulā praecidere, Cels. 7, 33: vitem serrulā desecare, Col. Arb. 6, 4: manubriata, Pall. 1, 43, 2.