means A circuit component that opposes the flow of electric current, dropping voltage and limiting how much current passes through.

from From 'resist' plus the agent suffix '-or' that turns a verb into the thing that does it (compare 'conductor,' 'capacitor'). 'Resist' came through Old French 'resister' from Latin 'resistere' — 're-' (back) plus 'sistere' (to take a stand, to halt), so literally 'to stand back against.' A resistor, fittingly, is the part that stands its ground against the current.