legion

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The major unit of the Roman army consisting of 3,000 to 6,000 infantry troops and 100 to 200 cavalry troops.
2. n. A large military unit trained for combat; an army.
3. n. A large number; a multitude. See Synonyms at multitude.
4. n. A national organization of former members of the armed forces.
5. adj. Constituting a large number; multitudinous: Her admirers were legion. His mistakes were legion.

Century Dictionary and Cyclopedia

1. n. In Roman antiquity, a body of infantry not corresponding exactly to either the regiment or the army-corps of modern times, composed of different numbers of men at different periods, from 3,000 under the kings to over 6,000 under Marius, usually combined with a considerable proportion of cavalry. The ancient legion had 300 horse, and that of Marius about 700. Each legion was divided into ten cohorts, each cohort into three maniples, and each maniple into two centuries. The great power of the Roman legion was due to its rigid discipline and its tactical formation in battle, which was so open and flexible as to enable it to meet every emergency without surprise or derangement. It thus presented a strong contrast on the one hand to the unwieldy solidity of the Greek phalanx, and on the other to the confused and undisciplined state of other armies of the time. Compare maniple.
2. n. In French history, one of numerous military bodies so called at different periods. Foreign legions were employed by the kings from medieval times. A number of them were formed during the Revolution and under the first empire, of which one was maintained till a recent period. This body, called specifically the legion, made itself famous in Algiers and in the Crimea. There were also provincial legions in the sixteenth century.
3. n. Any distinct military force or organization comparable to the Roman legion.
4. n. An extraordinary number; a great multitude.
5. n. In zoology, a large group or series of animals, of indeterminate taxonomic rank, but generally of high grade. In Haeckel's system, for example, the legion intervenes between the subclass and the order, and corresponds to what is usually called a superorder.
6. To enroll or form into a legion.

Wiktionary

1. adj. Numerous; vast; very great in number; multitudinous.
2. n. military The major unit or division of the Roman army, usually comprising 3000 to 6000 infantry soldiers and 100 to 200 cavalry troops.
3. n. A large military or semimilitary unit trained for combat; any military force; an army, regiment; an armed, organized and assembled militia.
4. n. A national organization or association of former servicemen, such as the American Legion, founded in 1919.
5. n. A large number of people; a multitude.
6. n. often plural A great number.
7. n. dated, taxonomy A group of orders inferior to a class; in scientific classification, a term occasionally used to express an assemblage of objects intermediate between an order and a class.

GNU Webster's 1913

1. n. (Rom. Antiq.) A body of foot soldiers and cavalry consisting of different numbers at different periods, -- from about four thousand to about six thousand men, -- the cavalry being about one tenth.
2. n. A military force; an army; military bands.
3. n. A great number; a multitude.
4. n. (Taxonomy) A group of orders inferior to a class.

WordNet 3.0

1. n. archaic terms for army
2. n. a vast multitude
3. n. association of ex-servicemen
4. n. a large military unit
5. adj. amounting to a large indefinite number