To keep from being damaged, attacked, stolen, or injured; guard. See Synonyms at defend. To help (domestic industry) with tariffs or quotas on imported goods. To assure payment of (drafts or notes, for example) by setting aside funds. Sports To attempt to hold (a lead) by playing careful defense and avoiding risky plays. Baseball To swing at a pitch near (home plate) in order to avoid being called out on strikes. Baseball To swing at a pitch so as to give (a base runner) a better chance of advancing.