|Definition - A singular noun that stands for a collection of things.|
(1) a flock of seagulls
(2) a bunch of idiots
(3) a batch of cookies
(4) a group of Liberals
Oxford English Dictionary - The term's first citation is from 1520:
"The nominatyue case of the nowne collectiue."
( Whitinton Vulg. (1527) 6)