Entry 2 senses Webster, 1913 Federation /fĕdˌ-ẽr-āsh'-ən/ · Fed·er·a·tion · IPA /ˌfɛdəˈɹeɪʃn̩/ 01 n. The act of uniting in a league; confederation. 1. The act of uniting in a league; confederation. 2. A league; a confederacy; a federal or confederated government.