To deliberately hide facts or information

Hide
- The authorities tried to hide the facts from the people.
- I feel sure there's something about her past that she's trying to hide from me.
- He tried to hide his addiction from his father.

Conceal
- She concealed any evidences of her father’s murders.
- The authorities concealed the facts of the CIA involvement in the uprising.
- He concealed the truth from her.

Keep something secret
To deliberately not allow somebody knows a subject or an event:

- The authorities told me that you must keep the event secret.
- The resupply effort was probably kept secret from Congress.
- They kept the plan secret from other people.

Suppress
To prevent someone from knowing information or facts:

- The government tried to suppress the book because of the information it contained about the security services.
- At no time did they try to persuade me to suppress the information...
- Police were accused of suppressing evidence that might have proved that the men were innocent.
- The CIA has often tried to suppress reports that are embarrassing to the agency.

Cover up
To conceal evidence of wrongdoing, error, incompetence or other embarrassing information:

- He decided to cover up his apartment's ugly kitchen with portable mats rather than install permanent flooring..
- They tried to cover up their own inabilities and errors.
- When Caroline visits her handsome ex-beau at his office, she tries to cover up her attraction to him.
- A lot of good dialogue in films is the lies people tell to cover up what they're really feeling.
- I was amazed that the building contractors we hired tried to cover up the problems they had.

Hush up
To keep something immoral or dishonest secret and from public knowledge by authorities; suppress mention of:

- The scandal has been discussed by the politburo, although the authorities have tried to hush it up...
- The Ministry desperately tried to hush up the whole affair.
- The whole affair was hushed up by the government.
- Did the CIA hush up top-secret operation against Al-Qaeda? -
- It is at the behest of New Delhi that a desperate attempt is being made to hush up the case.

Cover your tracks
To be careful not to leave any signs or evidence that show know where you have been or what you have doing because you want to keep it a secret, usually because it is illegal:

- Roberts covered his tracks by throwing the knife in the river and burying his wife's body.
- He tried to cover his tracks by burning all the documents.
- They moved constantly and furtively, covering their tracks and contacting nobody.

Draw a veil over sth
A formal word meaning to hide or avoid discussing an unpleasant event or something happened in the past because it could cause trouble or make someone embarrassed:

- I think we should draw a veil over this conversation and pretend it never happened.
- Louise drew a veil over the accounting errors.
- It looked as if Luke's pride had allowed him to draw a veil over last night's final moments, and she was grateful for it.
- Think it best to draw a veil over the whole incident.
- Both sides sought to draw a veil over the argument.

Sweep or brush something under the carpet (British, American & Australian)/Sweep something under the rug (American & Australian)
To try to keep a problem, difficulty, mistake or an unpleasant thing secret in the hope that it will be forgotten or ignored:

-For a long time they tried to sweep under the carpet the crime.
-The real issues are just swept under the carpet and ignored.
-The problem is usually ignored or swept under the carpet.
-Refuse to sweep difficulties under the carpet but sort things out even when it is painful.
-We knew that it wouldn't just go away if we swept it under the carpet.
-The authorities tried to sweep the scandal under the carpet.

Keep something under wraps
keep something hidden and secret, not show or talk about Details of  it:

- They kept the information under wraps

- The judge kept the proceedings under wraps.

- The project has been kept under wraps for years.
- Details of the police operation are being kept under wraps.

- Many buyers preferred to keep their identities under wraps.

Keep something dark
A British word meaning to keep something secret and hidden from other people:

- I have a promotion but keep it dark.
- A retired teacher kept his wife murder secret for more than two decades .
- They kept their political activities dark.

Keep somebody in the dark also leave somebody in the dark
To intentionally conceal information from someone. Either to avoid confrontation or to gain from the other’s lack of information:

- Congress complained about being kept in the dark about the peace talks.
- When it comes to keeping something secret, the plan should be to keep in the dark.
- Council has kept us in the dark over plan.
- They kept me in the dark about their plans
- Public kept in the dark about talks on North American integration
- Liberal Catholic bishops kept in the dark over secret talks ...