late 14c., in reference to ancient Rome, from Latin circus "ring, circular line," which was applied by Romans to circular arenas for performances and contests and oval courses for racing (es [..]

a travelling show with acrobats and animals and clown who do all sorts of tricks

tsirk

(n) a travelling company of entertainers; including trained animals(n) a performance given by a traveling company of acrobats, clowns, and trained animals(n) a frenetic disorganized (and often comic) [..]

A combined interest rate and currency swap.

In WW II, a fighter-bomber mission whose primary goal was to force the German fighter defenses to come up and engage. Usually consisted of a small bomber force and heavy fighter escort.

a railroad, as in go join the circus.

British Intelligence (MI6) Competition

A traveling company of performers that may include acrobats, clowns, trained animals, and other novelty acts, that gives shows usually in a circular tent. ''The circus will be in town next week.'' [..]

Harrier (bird) * Circus (genus)