Idioms for everyone.

According to , http://www.edict.com.hk/vlc/idioms/idiomdef.htm  , an idiom is'

‘A group of words with a meaning of its own that is different from the meanings of each separate word put together’
                                                - Longman Dictionary of Contemporary English

Here are some examples of idioms taken from http://useit.vn/content/view/686/122/lang,english/

If you are chicken, you are not brave enough to do something.

Come on, Hisham, don't be such a chicken, sing us a song.

..to have butterflies in your stomach.

Very nervous or excited before doing something important such as giving a speech and taking a test.

I know you have butterflies in your tummy before your presentation.

...to get cold feet

If you get cold feet, you become afraid to do something that you planned to do or agreed to do.

If a person is a couch potato, he/she is not active and spends most of his/her time sitting and watching TV. 

With the World Cup coming soon, Ameen is going to be a couch potato.

To eat your words is to admit that what you said was wrong.

They had to eat their words when the truth was revealed.

Dear John is a letter from a woman to her boyfriend or husband telling him that she doesn't love him anymore.

Poor guy---he was down in the dumps (see below) after receiving a dear john letter from his girl friend.

If you are down in the dumps, you feel very sad and miserable. You don't have much interest in life.

There's nothing in the fridge, so lets eat out tonight.

...make head nor tail..

I can't make head nor tail of what thet lecturer wants us to do as he keeps changing his mind !

So, these are just some example from the link I provided above. Hop on to it as there are more to find out !