from: Wikipedia

Wikipedia defines an idiom as
"... a common word or phrase with a culturally understood meaning that differs from what its composite words' denotations would suggest. 
For example, an English speaker would understand the phrase "kick the bucket" to mean "to die" – as well as to actually kick a bucket. Furthermore, they would understand when each meaning is being used in context. 

An idiom is not to be confused with other figures of speech such as a metaphor, which invokes an image by use of implicit comparisons (e.g."the man of steel" ); a simile, which invokes an image by use of explicit comparisons (e.g."faster than a speeding bullet"); and hyperbole, which exaggerates an image beyond truthfulness (e.g., like "missed by a mile" ). Idioms are also not to be confused with proverbs, which are simple sayings that express a truth based on common sense or practical experience."

Notable Idioms In English

A situation or information that is unpleasant but must be accepted.

Anything that is common, inexpensive, and easy to get or available any where.

A hidden or secret strength, or unrevealed advantage.

A metaphor for a fatal weakness in spite of overall strength.

To further a loss with mockery or indignity; to worsen an unfavorable situation.

Listening intently; fully focused or awaiting an explanation.

Clumsy, awkward.

Without any hesitation; instantly.

Looking in the wrong place.

One made powerless or ineffective, as by nerves, panic, or stress.

To treat a topic, but omit its main points, often intentionally or to delay or avoid talking about something difficult or unpleasant.

To take on more responsibility than you can manage.

To endure a painful or unpleasant situation that is unavoidable.

Casual Euphemism for dying or death.

A saying from the theatre that means "good luck."

To work late into the night, alluding to the time before electric lighting.

To say things intended to harass.

To achieve through instinct or do something without advance preparation.

Narrowly; barely. Usually used in regard to a narrow escape from a disaster.

To declare the end of a task.

To chat idly or generally waste time talking.

An area of vulnerability

To become silent; to stop talking, to shut up.

To display aloofness and disdain.

A lazy person who watches TV a lot.

To dance

To pass gas, fart, break wind

To succeed; to come up to expectations.

"Don't have a cow "Don't overreact.

Make a telephone call; to be an informant.

In good physical health.

"For a song"Almost free. Very cheap.

Covering a complete range; comprehensively.

Make from original ingredients; start from the beginning with no prior preparation

To take offense; to get worked up, aggravated, or annoyed"

Have a blast"
To have a good time or to enjoy oneself.

Someone can perceive things and events that are outside of their field of vision.

To leave.

"Hit the sack "/sheets/hay
To go to bed.

Euphemism for dying or death.

To reveal a secret.

"Off one's trolley" or "Off one's rocker"
Crazy, demented, out of one's mind, in a confused or befuddled state of mind, senile.

To escape a situation of responsibility, obligation, or (less frequently) danger.

A job, task or other activity that is pleasantly easy – or, by extension, simple.

Euphemism for dying or death.

"To tease or to joke by telling a lie.

"Euphemism for dying or death.

To create a disturbance and cause trouble.

"Right as rain"
Needed, appropriate, essential, or hoped-for and has come to mean perfect, well, absolutely right.

To screw up; to fail in dramatic and ignominious fashion.

"Shoot the breeze"To chat idly or generally waste time talking.

Euphemism for dying or death.

Reveal someone's secret.

To arrive just on time.

To be particularly bad, objectionable, or egregious.

To be especially good or outstanding.

Both good and bad times.

To express scorn or to disregard.

To dance

Feel sick or poorly

That is very true; expression of wholehearted agreement

Cat nap
Short sleep/nap. A nap is a short sleep actually.