1. A large public entertainment, typically presented in one or more very large tents or in an outdoor or indoor arena, featuring exhibitions of pageantry, feats of skill and daring, performing animals, etc., interspersed throughout with the antics of clowns.
2. A troupe of performers; especially, a traveling troupe, that presents such entertainments, together with officials, other employees, and the company's performing animals, traveling wagons, tents, cages, and equipment.
3. A circular arena surrounded by tiers of seats, in which public entertainments are held; arena.
4. Anything resembling the Roman circus, or arena, as a natural amphitheater or a circular range of houses.

The modern circus owes its name to the amusements of ancient Roman times. The Latin word circus, which comes from the Greek word kirkos, “circle, ring”, referred to a circular or oval area enclosed by rows of seats for spectators.

In the center ring, a variety of events were held, including chariot races and gladiatorial combats, spectacles in which bloodshed and brutality were not uncommon.

Our modern circus, which dates to the end of the 18th century, was originally an equestrian spectacle, but the trick riders were soon joined in the ring by such performers as ropedancers, acrobats, and jugglers.

Even though the circular shape of the arena and the equestrian nature of some of the performances are carried over from its Roman namesake, the modern circus has little connection with its brutal namesake of long ago.