An idiom is a phrase that makes no sense unless you know the definition. Sleek is a word.
"To be" is not an idiom - it's a verb.
The idiom "apple shiner" means the teacher's pet.
Pest is not an idiom. It's a word.
My Favorite IDIOM Is, When Pigs Fly.
It is actually an idiom.
The word "sleek" can function as an adjective or a verb. As an adjective, it describes something smooth and glossy. As a verb, it means to make something smooth or glossy.
Idiom is correct.
A snake is sleek. Most sleek is the Black Mamba.
Sleek and red are both adjectives.She prefers a sleek hairstyle.He prefers the red sofa.They prefer the sleek red Ferrari.
the boy has sleek hair
a sleek car is glossy paint job
what is a idiom about a cat
a sleek car is glossy paint job
Sleek and gracefuf
Me and my hair are sleek today.
"To be" is not an idiom - it's a verb.
An idiom misuse is to use and idiom in a wrong way that doesn't make sense.