An idiom is a phrase that conveys a different meaning than the individual words would imply, given their official definition in a dictionary.
One such idiomatic expression is:
It’s raining cats and dogs outside.
Obviously, there are not multiple domestic animals falling out of the sky, but it’s raining so hard that it commands your attention as if cats and dogs were raining down upon you.
Idiomatic expressions can certainly make your writing more colorful, but you have to be careful, because some people from other countries, cultures, or native languages may not be familiar with that phrase and may mistake its meaning.
This is particularly true in the oil industry, where virtual teams from different lands and languages often work together on a project.
Here is a valuable resource for those who may run across an unfamiliar idiomatic expression:
This website lists 3,416 idioms used in the English language, along with their meanings.
Here are a few examples that could be misinterpreted:
Make a mint = make a lot of money, not manufacture an after-dinner confection
Save face = protect one’s reputation, not wear a protective face shield
Fire away = you are free to ask questions, not shoot a gun at me or place a flame at a distance
If you are thinking about using an idiom in your writing, first consider your audience and whether they are likely to understand it.
If they share the same culture and language as you, then go ahead and give it a whirl (= try it).
If your audience is more international in composition, consider rewording the sentence — without using idioms — to make your meaning clear.