| business-like |
| caliginous(dull, dark, gloomy) |
| callous(adjective, calm, restrained, subdued, impassive) |
| casual(adjective, calm, restrained, subdued, impassive) |
| cloudy(dull, dark, gloomy) |
| cold-blooded(rational, straightforward, down-to-earth) |
| cold fish(expression, adjective, calm, restrained, subdued) |
| common(adjective, reasonable, sensible, sober, practical) |
| common-sense |
| commonsense(adjective, reasonable, sensible, sober, practical) |
| commonsensical(practical, realistic) |
| consequential(big, heavy, substantial) |
| considerable(big, heavy, substantial) |
| constant(adjective, thoughtful, sober, serious, sincere) |
| cool as cucumber(expression, idiom, calm, quiet, cool) |
| critical(big, heavy, substantial) |
| crucial(big, heavy, substantial) |
| cumbersome(big, heavy, substantial) |
| cumbrous(big, heavy, substantial) |
| decorous(adjective, calm, quiet, cool, sober) |