Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
The word iaculus could not be parsed. Trying a normal dictionary lookup:
jăcŭlus, a, um, adj. [jacio], that is thrown (mostly subst.). So, rete jaculum and simply jaculum, a casting-net, fishingnet, Plaut. Truc. 1, 1, 14; id. As. 1, 1, 86; cf.: hi jaculo pisces, illi capiuntur ab hamis, Ov. A. A. 1, 763.
Also of the net of the gladiator retiarius, Isid. Orig. 18, 54.
Hence, subst.: jăcùlus, i, m.