Syncope s => vis
Syncopated perfect often drops the 'v' and contracts vowel
subiv.issemus V 6 1 PLUP ACTIVE SUB 1 P
subeo, subire, subivi(ii), subitus V INTRANS [XXXAO]
go/move/pass/sink/extend underneath/into; climb/come/go up, ascend; steal in on
place/be placed under/in support; come up w/aid; assume a form; undergo, endure

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.