| Idiom | Meaning | Example | 
| clouds on the horizon | 
a problem has appeared, something is wrong, the sky isn't blue
 | 
We have achieved our goals, but there are clouds on the horizon.
The government is going to cancel our funding.
 | 
| clued in | 
aware, in the know, with it
 | 
"How do you get clued in?" "You watch and listen, man."
 | 
| clueless | 
not informed, ignorant, not with it
 | 
When I don't know the answer, I try not to look clueless.
 | 
| clunker | 
a car that is in poor condition, a beater
 | 
Uncle Blair has bought another clunker - an old Pontiac.
 | 
| clutch hitter (baseball) | 
(See a clutch hitter)
 | 
 | 
| clutz | 
(See klutz)
 | 
 | 
| cock and bull [B] | 
nonsense, bull, BS [B]
 | 
Don't believe that cock-and-bull story about Bigfoot.
 | 
| cocky | 
proud, smartass
 | 
"Why is Len acting so cocky?" "He won the Frisbee contest."
 | 
| cocoon | 
stay inside your home to feel comfortable and safe
 | 
We don't want to go out tonight. We feel like cocooning.
 | 
| coffee talk | 
conversation while having coffee, water-cooler...
 | 
I don't believe Sally's pregnant. It's just coffee talk, just gossip.
 |