.45 Meaning of .45 in English .45 /ˌfɔːti ˈfaɪv $ ˌfɔːrti-/ BrE AmE noun [countable] a pistol (=small gun) that takes ↑ bullet s which are .45 ↑ inch es in ↑ diameter Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012