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.
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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