1、(as) black as (one's) hat
Completely black; totally without light or color.
The basement gives me the creeps, it's as black as my hat down there!
2、a black day
a day when something very unpleasant or sad happens (usually + for ).
发生了一些很不开心或悲伤事情的一天（常用作a black day for）。
When we heard the news that David Bowie had died, we knew it was going to be a black day for all of his loyal fans.
3、be in the black
If a bank account is in the black, it contains some money, and if a person or business is in the black, they have money in the bank and are not in debt.
如果一个银行账户in the black，说明里面还有一些钱。如果一个人或企业是in the black，那么他们在银行还有存款，没有负债。
Incredibly, we're still in the black after our holiday.
4、back the black stump
In or of an extremely remote, isolated, and/or uncivilized location, usually meaning the Australian outback."Black stump" is used colloquially as an imaginary marker of the edge of civilized settlement, though the origin of the term is uncertain. Primarily heard in Australia.
There are many people who still live back of the black stump, lacking access to medical care and other basic social services.
5、the new black
used to say that something is the most popular or fashionable colour or thing at the moment
Designers say that green is the new black.
6、devil is not so black as he is painted
No one is as bad as people say he is. (Implies that people are saying too many bad things about someone.)
I can't believe that actress is as coldhearted as the gossip columns say she is. The devil is not so black as he is painted.
7、give a black eye to (someone or something)
To make someone or something look bad; to damage one's reputation.
That food critic's negative review really gave a black eye to my restaurant.
8、as clear as black and white
Of the utmost clarity; clearly defined or differentiated; without any room for confusion, ambiguity.
Love isn't always as clear as black and white, you know. You have to accept that there are many gray areas in relationships.
The case made by the government seems as clear as black and white: raise taxes to pay for public amenities.
9、the Black Maria
A police vehicle, typically one carrying prisoners.
Man, there's the Black Maria. Looks like I'm headed to a different jail.
They just threw Billy in the back of a Black Maria and hauled him off to the police station!
1) [for lights] to go out.
Suddenly the lights blacked out.
The power went dead and everything blacked out.
2) to pass out; to become unconscious.
After I fell, I must have blacked out.
I think I am going to black out.