10 letters · 14 points in Scrabble
noun any substance that propels
adjective tending to or capable of propelling
originFrom propel + -ent; originally from Latin prōpellēnt-, from prōpellēns, from prōpellō. Less common than propellant despite being more correct from an etymological viewpoint.
Etymology from Wiktionary, CC BY-SA 3.0