This week's theme: unusual words. succedaneum (suk-si-DAY-nee-uhm) noun A substitute. [From Latin succedere (to succeed), from suc- (a variant of sub-, used before c) and cedere (to go). Ultimately from Indo-European root ked- (to go or yield) that's also the ancestor of exceed, secede, proceed,... Sign in to see full entry.