legion
n. countablen. a very large group of people or things. It can also mean a large unit of soldiers in the army of ancient Rome.
n. a vast multitude of people or things; historically, a major unit of the Roman army consisting of several thousand soldiers. Often used in the plural to emphasize scale.
Legions of fans waited outside the stadium for the singer.
The company faced legions of complaints after the software update caused thousands of computers to crash.
While the Roman legion remains a symbol of ancient military discipline, the term now more commonly describes the overwhelming number of volunteers required to staff such a massive event.
Attested (in Middle English, as legioun) around 1200, from Old French legion, from Latin legiō, legionem, from legō (“to gather, collect”); akin to legend, lecture. Doublet of León, which was borrowed from Spanish. Generalized sense of “a large number” is due to an allusive phrase in Mark 5:9, "My name is Legion, for we are many".
Often used in the plural form 'legions of' followed by a plural noun to indicate a vast number.