legion

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The major unit of the Roman army consisting of 3,000 to 6,000 infantry troops and 100 to 200 cavalry troops.
• noun A large military unit trained for combat; an army.
• noun A large number; a multitude. synonym: multitude.
• noun A national organization of former members of the armed forces.
• adjective Constituting a large number; multitudinous.

from The Century Dictionary.

• To enroll or form into a legion.
• noun 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.
• noun In French history, one of numerous military bodies so called at different periods.
• noun Any distinct military force or organization comparable to the Roman legion.
• noun An extraordinary number; a great multitude.
• noun In zoology, a large group or series of animals, of indeterminate taxonomic rank, but generally of high grade.

from the GNU version of the Collaborative International Dictionary of English.

• noun (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.
• noun A military force; an army; military bands.
• noun A great number; a multitude.
• noun (Taxonomy) A group of orders inferior to a class.
• noun an order instituted by the French government in 1802, when Bonaparte was First Consul, as a reward for merit, both civil and military.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Numerous; vast; very great in number; multitudinous.
• noun military The major unit or division of the Roman army, usually comprising 3000 to 6000 infantry soldiers and 100 to 200 cavalry troops.
• noun A large military or semimilitary unit trained for combat; any military force; an army, regiment; an armed, organized and assembled militia.
• noun A national organization or association of former servicemen, such as the American Legion, founded in 1919.
• noun A large number of people; a multitude.
• noun often plural A great number.
• noun 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.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun archaic terms for army
• noun a vast multitude
• noun association of ex-servicemen
• noun a large military unit
• adjective amounting to a large indefinite number