Czech Republic

 Costa Rica

The Colbert Report

critical reading on the SAT

Colorado Rockies, Major League Baseball team

caloric restriction

Celtic Reconstructionism

Consumer Reports, American magazine

critically endangered species

Camp Ridgecrest for Boys

Comfort room

Constitutional routes

Crawford County, Kansas

compression ratio

carriage return

challenge-response spam filtering

challenge rating, Dungeons and Dragons. See Book of Challenges

College Republicans

change request

Comptes rendus - French for reports or proceedings; often used in title of publications, most notably the Comptes rendus de l'Académie des sciences (Proceedings of the (Paris) Academy of Sciences).

Computed radiography

Castle Rock

cognitive robotics

CR postal area

concentration ratio

Český Rozhlas

Critical Review, several publications by this name

Cree language (ISO 639 alpha-2)

Chromium (chemical symbol)

CR gas (dibenzoxazepine)

Creatine, a molecule found in myocytes

Conrail (AAR reporting mark)

Cedar Rapids,Iowa

Coral Sea Islands (FIPS country codes and obsolete NATO country code)

cognitive radio, an outgrowth of software-defined radio

credit, in accounting

Colorado Rockies (NHL), former NHL team that has since relocated and became the New Jersey Devils