Word mod ops/obs
An initial 'ops' may be rendered by 'obs'
obstacul.um N 2 2 NOM S N
obstacul.um N 2 2 VOC S N
obstacul.um N 2 2 ACC S N
obstacul.um N 2 2 GEN P N uncommon
obstaculum, obstaculi N (2nd) N [XXXDX] lesser
obstacle, obstruction; that which stands in the way;

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.