Propugnation is a rare word that means "defense" or "support". Although it isn't used often, there are many synonyms you can use to convey the same meaning. Some of these synonyms include advocacy, backing, championing, promotion, bolstering, and protection. Other words that can work as synonyms for propugnation include reinforcement, encouragement, fortification, help, and assistance. These words all refer to ways of supporting or protecting something or someone. So, the next time you need to express the idea of defense or support, you can use any of these words as a substitute for propugnation.