We also often use "bomb" this way when talking about movies, plays or performing. For example, if a comedian is on stage telling jokes but no one is laughing, you can say his jokes are bombing. Afterward, if you are feeling very mean, you could say to him, "Wow, you really bombed."

Now, let's say nobody goes to the new superhero movie, you can say it bombed at the box office. The box office is where people buy their movie tickets. In this case, they were buying tickets for a dud or a flop. These two words are often used to describe a form of entertainment that failed in its purpose -- to entertain.​

Even a party that bombs can be called a dud or a flop. And if a class you are taking is boring or useless, you could call it a "a real dud."

Now, let's go back to bombing.

Please take note that when the word "bomb" is a verb, it means to fail.

As a slang expression, however, “the bomb” often describes something really good. For example, if a high school student wears a new pair of sneakers to school, his friends could say, "Those shoes are the bomb!" That means they are great -- in a cool, awesome kind of way.

But please be careful: using “the bomb" this way is extremely casual and would not be appropriate to use in a formal situation. For example, let's say your boss wears a new suit to an important meeting. It might not be a good career move to say to her, "That outfit is the bomb! You look awesome!"

And making comments about a bomb at a U.S. airport could get you arrested.

So, as we said, be careful!

Now, let's talk about expressions to use when you do something really well.

Let's say you did well on a test. You got 100% correct. You aced it! You can also say that you passed with flying colors.

The last expression might make you think of a big celebration — like maybe your parents celebrated your passing grade by lighting colorful fireworks.

But you would be wrong.

Word experts seem to agree that the expression "to pass with flying colors" comes from the military. In this case, “pass” doesn’t mean to succeed, but to travel. And “colors” doesn’t mean shades like red or blue, but flags.

According to the website The Phrase Finder, “pass with flying colors” originally describes winning ships sailing into port “with flags flying from all the mastheads.” By around 1700, the phrase was being used to describe any kind of victory.

That means you can use "pass with flying colors" when you are being graded on a test or course, but also in a situation that is out of your control -- such as a medical exam.

Let's say you are nervously waiting in a doctor's exam room for the results of a blood test. The doctor may come in and say, "Don't worry! I'm looking at the results of your blood test and you passed with flying colors!" It's not as if you studied for your blood test and then did well on it. So, this is the doctor's way of being lighthearted or funny.

comedian – n. a person who performs in front of an audience and makes people laugh by telling jokes or funny stories or by acting in a way that is funny : an actor who plays roles that make people laugh
dud – n. something that does not do what it is supposed to do : something that is a complete failure : The movie was a box office dud. [=few people went to see the movie]
flop – n. informal : to fail completely
cool – adj. very fashionable, stylish, or appealing in a way that is generally approved of especially by young people
awesome – adj. informal : extremely good
casual – adj. designed for or permitting ordinary dress, behavior, etc. : not formal
formal – adj. requiring or using serious and proper clothes and manners
outfit – n. a set of clothes that are worn together
ace – v. US, informal : to earn a very high grade on (an examination) : to get a grade of A on (an examination)
masthead – n. the top of a ship's mast
lighthearted – adj. having or showing a cheerful and happy nature