| n. 1.  The major unit of the Roman army consisting of 3,000 to 6,000 infantry troops and 100 to 200 cavalry troops. 2.  A large military unit trained for combat; an army. 3.  A large number; a multitude. See Synonyms at  multitude. 4.  often  Legion A national organization of former members of the armed forces. adj.  Constituting a large number; multitudinous: Her admirers were legion. His mistakes were legion. [Middle English legioun, from Old French legion, from Latin legiō, legiōn-, from legere, to gather; see  leg- in the Appendix of Indo-European roots.] | 
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