1.
a. A closed, usually circular line that goes around an object or area. b. The region enclosed by such a line. See synonyms at circumference.
2.
a. A path or route the complete traversal of which without local change of direction requires returning to the starting point. b. The act of following such a path or route. c. A journey made on such a path or route.
3. Electronics. a. A closed path followed or capable of being followed by an electric current. b. A configuration of electrically or electromagnetically connected components or devices.
4. a. A regular or accustomed course from place to place; a round: a salesperson on the Detroit-Minneapolis-Chicago circuit; a popular speaker on the lecture circuit. b. The area or district thus covered, especially a territory under the jurisdiction of a judge in which periodic court sessions are held.
5. a. An association of theaters in which plays, acts, or films move from theater to theater for presentation. b. A group of nightclubs, show halls, or resorts at which entertainers appear in turn. c. An association of teams, clubs, or arenas of competition: the downhill ski circuit.
[Middle English, circumference, from Old French, from Latin circuitus, a going around from past participle of circumīre, to go around : circum-, circum- + īre, to go.]