decum.arum NUM 2 0 GEN P F ORD
decum NUM [XXXCO]
10th - (ORD, 'in series'); (a/the) 10th (part) (fract w/pars?);
decum.arum N 1 1 GEN P F
decuma, decumae N (1st) F [XLXDO] lesser
tenth part/tithe; (offering/tax/largesse); tax/right to collect 10%; 10th hour

Credits:
This, our local install of the popular standby Whitaker's Words, is possible thanks to the resurrection of the venerable project at William Whitaker's Words, where you will also find extensive documentation. The corresponding GitHub repository is where you can submit issues about missing forms and analyses.
This web interface by Walter M. Shandruk.