Synonyms for Insure (same or very similar meaning)
WordNet sense 1 (protect by insurance):
cover, underwriteWordNet sense 2 (make certain of):
assure, ensure, guarantee, secureWordNet sense 3 (be careful or certain to do something; make certain of something):
ascertain, check, control, see, see to itFrom the ODE community, based on WordNetadd/edit