IDIOM

What is idiom?
Idioms exist in every language. An idiom is a word or phrase that is not taken literally, like “bought the farm” has nothing to do with purchasing real estate, but refers to dying. Idiom also refers to a dialect or jargon of a group of people, either in a certain region or a group with common interests, like in science, music, art, or business.
(Idiom atau disebut juga dengan ungkapan adalah gabungan kata yang membentuk arti baru di mana tidak berhubungan dengan kata pembentuk dasarnya).
Example

1. She is pulling my leg. - to pull someone's leg means to tease them by telling them something untrue.
2. When will you drop them a line? - to drop someone a line means to send a note to or call someone. 
3. You should keep an eye out for that. - to keep an eye out for something means to maintain awareness of it so  that you notice it as it occurs. 
4.  I can't keep my head above water. - to keep one's head above water means to manage a situation. 
5.  It's raining cats and dogs. - to rain cats and dogs means to rain very heavily (a downpour).

Common Idioms
Some idioms are used by most people that speak English; others are used by a more select group.
Common idioms that refer to people include:

• A chip on your shoulder - means you are holding a grudge
• High as a kite - means you are drunk or on drugs
• Sick as a dog - means you are very ill

Idioms that refer to your actions would be:

• Rub someone the wrong way - meaning to annoy or bother
• Jump the gun - would mean to be doing something early
• Pay the piper - means you need to face the consequences of your actions

Some idioms use color words to convey other meanings. For example, there are several that use the word “blue:”

• “The blues” can refer to both a style of music and feeling sad.
• If something occurs rarely, it is said to happen “once in a blue moon”, because a blue moon is two full moons in one month, which doesn’t happen often.
• “Out of the blue” means something happens that was unexpected.  

Learning a Language with Idioms
Because of idioms, learning a language can be complicated. After you can conjugate verbs, and know a lot of words, you may still have difficulty speaking the language with native users.
This is partly due to the use of idioms and would also depend of which region of a country you were in. Idiom usage is not just regional, but also varies according to people’s interests and social groups.
The best way to pick up on the meaning of certain idioms would be to converse with people and ask them for a clarification of the idiom if you are not clear about the idiom they used. There are also sites on the Internet which will help explain the meaning of idioms.

Idioms Around the Globe
There are certain things that happen in every culture and there are idioms to deal with them.

• In Norwegian and Czech, “walking around hot porridge” refers to beating around the bush, which is also an idiom meaning not getting to the point.
• If you are in Italy or Turkey and you say you are “as hungry as a wolf” then you are starving.

If it is raining in large amounts, most cultures have an interesting way of saying that:

• In English, it would be “raining cats and dogs”
• In Africa, they might say “it's raining old women with clubs”

• Many languages refer to heavy rain as coming in buckets or as rain coming out of a bucket.

• In Norway they say “it's raining female trolls”
• The Irish say “it's throwing cobblers knives”

Comparing idioms between countries can also be interesting:

• In Finnish, “with long teeth” means you are doing something that you really don’t want to do
• In French, “to have long teeth” means you are ambitious.

The key to understanding the local idioms is to listen carefully and to ask questions of local speakers.

Idioms In the Arts
There are many idioms in the field of music.

• If you “fine tune” something, you make small improvements to it.
• “Changing your tune” means changing your mind.
• If you are “whistling Dixie” or “whistling in the dark” you are overly positive about something.
• If you try and make a decision too early without knowing all the facts, people may tell you that “it’s not over ‘till the fat lady sings.”

Drama and dance have idioms, too, like:

• “Break a leg” means good luck.
• If you are a “ham” you overact.
• If you say, “it takes two to tango” you mean that more than one person is at fault or involved.
• If you “tap dance” your way out of a sticky situation, then that implies that you get out of it in a clever way.
• Being “in the spotlight” means you are the center of attention.

reference:
https://en.wikipedia.org/wiki/Idiom 
http://examples.yourdictionary.com/idiom.html