Just when foreigners think they've mastered the English language, they could be in for a rude awakening upon their first time engaging in a conversation with an American. Not all expressions are taught in textbooks or apps on their smartphones.

The English grammar is loaded with inconsistent rules and idioms that can throw off tourists who will understandably interpret every word literally. For example, If you ask them to "shoot the breeze" they may be inclined to admit they don't own any weapons. Fair enough.

The Insider provided examples of idioms along with their meaning. And revisiting them closely confirms the English language is a very strange language indeed.

When a task is easy to undertake, it's "a piece of cake." The phrase is most likely from "The Primrose Path," a1935 poetry collection by American humorist Ogden Nash.

Her picture's in the papers now, and life's a piece of cake.

Shoving a whole cake in your mouth is a piece of cake.

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When fellow actors tell you "Break a leg," they're actually wishing you good luck, not cursing you to invoke a tibia snap.

The expression is supposedly derived from the German phrase – Hals- und Beinbruch, which translates to "neck and leg break," which is a corruption of a Hebrew blessing meaning "success and blessing."

Once more with feeling...

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When something is worthless, it's "for the birds." The term was first used as slang during World War II.

Even the remote was for the birds.

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When a major secret is revealed, "the cat's out of the bag."

The first known use of the term came from a book review published in a 1760 issue of The London Magazine, where the critic wrote:

We could have wished that the author had not let the cat out of the bag.

The word (and cat) is out!

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Twitter had some contributions to other unusual phrases.

This is a popular term circulating among millennials and it has nothing to do with temperature.

H/T - Flickr, MentalFloss, Twitter