What does « To hide / To conceal » mean in the Quran?

Indeed, those who conceal what We sent down of clear proofs and guidance after We made it clear for the people in the Scripture - those are cursed by Allah and cursed by those who curse,

Indeed, they who conceal what Allah has sent down of the Book and exchange it for a small price - those consume not into their bellies except the Fire. And Allah will not speak to them on the Day of Resurrection, nor will He purify them. And they will have a painful punishment.

Divorced women remain in waiting for three periods, and it is not lawful for them to conceal what Allah has created in their wombs if they believe in Allah and the Last Day. And their husbands have more right to take them back in this [period] if they want reconciliation. And due to the wives is similar to what is expected of them, according to what is reasonable. But the men have a degree over them [in responsibility and authority]. And Allah is Exalted in Might and Wise.

And if you are on a journey and cannot find a scribe, then a security deposit [should be] taken. And if one of you entrusts another, then let him who is entrusted discharge his trust [faithfully] and let him fear Allah, his Lord. And do not conceal testimony, for whoever conceals it - his heart is indeed sinful, and Allah is Knowing of what you do.

O People of the Scripture, why do you confuse the truth with falsehood and conceal the truth while you know [it]?

And that He might make evident those who are hypocrites. For it was said to them, "Come, fight in the way of Allah or [at least] defend." They said, "If we had known [there would be] fighting, we would have followed you." They were nearer to disbelief that day than to faith, saying with their mouths what was not in their hearts. And Allah is most Knowing of what they conceal -

And [mention, O Muhammad], when Allah took a covenant from those who were given the Scripture, [saying], "You must make it clear to the people and not conceal it." But they threw it away behind their backs and exchanged it for a small price. And wretched is that which they purchased.

Who are stingy and enjoin upon [other] people stinginess and conceal what Allah has given them of His bounty - and We have prepared for the disbelievers a humiliating punishment -

That Day, those who disbelieved and disobeyed the Messenger will wish they could be covered by the earth. And they will not conceal from Allah a [single] statement.

And when they come to you, they say, "We believe." But they have entered with disbelief [in their hearts], and they have certainly left with it. And Allah is most knowing of what they were concealing.

Not upon the Messenger is [responsibility] except [for] notification. And Allah knows whatever you reveal and whatever you conceal.

O you who have believed, testimony [should be taken] among you when death approaches one of you at the time of bequest - [that of] two just men from among you or two others from outside if you are traveling through the land and the disaster of death should strike you. Detain them after the prayer and let them both swear by Allah if you doubt [their testimony, saying], "We will not exchange our oath for a price, even if he should be a near relative, and we will not withhold the testimony of Allah. Indeed, we would then be of the sinful."

Indeed, He knows what is declared of speech, and He knows what you conceal.

There is no blame upon you for entering houses not inhabited in which there is convenience for you. And Allah knows what you reveal and what you conceal.

And a believing man from the family of Pharaoh who concealed his faith said, "Do you kill a man [merely] because he says, 'My Lord is Allah' while he has brought you clear proofs from your Lord? And if he should be lying, then upon him is [the consequence of] his lie; but if he should be truthful, there will strike you some of what he promises you. Indeed, Allah does not guide one who is a transgressor and a liar.