cor·don / ˈkôrdn/ • n. 1. a line or circle of police, soldiers, or guards preventing access to or from an area or building.2. an ornamental cord or braid.3. Archit. another term for stringcourse.• v. [tr.] (cordon off) prevent access to or from (an area or building) by surrounding it with police or other guards.

cordon.
1. String- or belt-course, usually a band, projecting slightly from a wall, normally used in connection with fortifications.

2. Slightly projecting step or riser at the lower edge of each part of a stepped ramp so that each section between steps has less of an inclination than the ramp as a whole (called scala cordonata or scala a cordoni), for surer footing. It is essentially a step-division in an inclined plane.

cordon cordon bleu a cook of the highest class. The term (in French, literally ‘blue ribbon’) is recorded from the mid 18th century; the blue ribbon once signified the highest order of chivalry in the reign of the Bourbon kings.
cordon sanitaire a guarded line preventing anyone from leaving an area infected by a disease and thus spreading it; the term is recorded from the 19th century.

cordon projecting course of stones XVI; line of military posts or police XVIII. — It. cordone, augm. of corda CORD; superseded by F. cordon.

Cordon

a continuous line or circle of persons or objects forming a barrier around a person, place, or building; a string or row of stones. See also chain.

Examples: cordon of admirers, 1854; of strike pickets; of police, 1883; cordon sanitaire; of troops.