| clean-timbered | | | |
| clean up | | | |
| clean up one's act | | | |
| clear blue water | | | |
| clear cut | | | |
| clear off | | | |
| clear one's lines | | | |
| clear the air | | | |
| clear the table | | | |
| click into gear | | | |
| climb down | | | |
| climb the walls | | | |
| clip it | | | |
| clip someone's wings | | | |
| clitlicker | | | |
| clock in | | | |
| clock is ticking | | | |
| clock the tea | | | |
| clog up | | | |
| close, but no cigar | | | |
| closed book | | | |
| close enough for government work | | | |
| close in on | | | |
| close one eye | | | |
| close one's eyes | | | |
| close one's eyes and think of England | | | |
| close one's mind | | | |
| close on the heels of | | | |
| close season | | | |
| closet case | | | |
| close the book on | | | |
| close the books | | | |
| close the face | | | |
| close the stable door after the horse has bolted | | | |
| close to home | | | |
| cloth | | | |
| clothespin vote | | | |
| cloud-headed | | | |
| cloud nine | | | |
| cloud seven | | | |
| clout list | | | |
| clue stick | | | |
| clusterfuck | | | |
| clutch artist | | | |
| clutches | | | |
| coals to Newcastle | | | |
| cobbler, keep to your last | | | |
| cock-and-bull story | | | |
| cock a snook | | | |
| cockblock | | | |
| cock cheese | | | |
| cock in the henhouse | | | |
| cock off | | | |
| cock of the roost | | | |
| cock of the walk | | | |
| cock one's toes | | | |
| coffee money | | | |
| coffee talk | | | |
| coil up | | | |
| coke dick | | | |
| cold cash | | | |
| cold chills | | | |
| cold comfort | | | |
| cold day in Hell | | | |
| cold fish | | | |
| cold hand | | | |
| cold hard cash | | | |
| cold-livered | | | |
| cold one | | | |
| cold shoulder | | | |
| cold snap | | | |
| cold treatment | | | |
| cold turkey | | | |
| collect dust | | | |
| collect one's thoughts | | | |
| comb-out | | | |
| comb through | | | |
| come a cropper | | | |
| come across | | | |
| come again | | | |
| come alive | | | |
| come along | | | |
| come a long way | | | |
| come apart at the seams | | | |
| come around | | | |
| come back from the dead | | | |
| come clean | | | |
| come down | | | |
| come down in stair rods | | | |
| come down to | | | |
| come down to earth | | | |
| come down to us | | | |
| comedy gold | | | |
| comedy of errors | | | |
| come first | | | |
| come forward | | | |
| come from a Cracker Jack box | | | |
| come from a good place | | | |
| come full circle | | | |
| come hell or high water | | | |