a moving force; impulse; stimulus

The grant for building the opera house gave impetus to the city's cultural life.

(broadly) the momentum of a moving body, esp. with reference to the cause of motion.

noun

block , check , hindrance

noun

catalyst , energy , goad , impulse , impulsion , incentive , incitation , incitement , momentum , motivation , power , pressure , push , spur , stimulant , urge , encouragement , fillip , inducement , prod , stimulation , stimulator , ambition , drive , force , stimulus