Synonyms for Fortify (same or very similar meaning)
WordNet sense 1 (enclose by or as if by a fortification):
fortWordNet sense 2 (prepare oneself for a military confrontation):
arm, gird, build upWordNet sense 3 (add alcohol to (beverages)):
lace, spikeWordNet sense 4 (make strong or stronger):
strengthen, beef upFrom the ODE community, based on WordNetadd/edit