"It's raining cats and dogs!"
That's an idiom (you can't take it literally)
***MERGE THIS QUESTION*** should be with "What are some examples of idioms" - see Related Question link below
"On the outs" IS an idiom! Many colorful expressions cover the subject of fallen out lovers, among them Splitsville and Pffft.
Idioms are a part of daily speech. They convey meaning quickly and are often easy to use and learned early on by native speakers. Idioms are also an important part in the process of "acculturation". According to Wikipedia: Acculturation is the exchange of cultural features that results when groups of individuals having different cultures come into continuous first hand contact. Idioms are pivotal in learning a new language. A learner of a second language is informally considered "advanced" when and if he/she masters the use of idioms.
Here is a link to some idioms. You can pick the "non-common" ones for yourself -- some people have heard certain idioms a lot and others have not heard the same ones, so you'll need to decide that part.
Moon Phrases or Idioms (http://dictionary.reference.com/browse/idiom) are phrases that refer to the moon, but use the reference in the way that other words are used in Idiomatic speech. Check this link for some common Moon Idioms and expressions that you may already know. http://home.hiwaay.net/~krcool/Astro/moon/moonwords/index.htm Some other idioms you may know are listed here: http://www.idiomsite.com/
Idiomatic expressions are essentially literary and not pictorial. There are some well illustrated, pictorial books titled " English Idioms [ in Business, in Sports, in Relationships, etc. ] or something similar, in bookstores at home and abroad. Try your local library or other book supplier.
There are many idioms and phrases for 'on the back burner'. Some idioms and phrases for 'on the back burner' include 'pushing aside' and 'procrastinating'.
One reason why some idioms are confusing because the way the sentences are worded
"Idioms for Being Afraid", "Idioms for Being Angry", "Idioms for Being Happy" are some examples of idioms found in the book "Found" by Margaret Peterson Haddix.
Some websites that have idioms written in them include The Free Dictionary, Cambridge Dictionary, and Phrases.com. These sites provide definitions and examples of idioms to help users understand their meanings and usage in context.
savvy, brainy