to cover: to spread or lay something over a thing so that it is no longer bare or exposed
At its core this word is about putting one thing over another so the thing underneath is hidden from sight. The same plain action runs through nearly every use, and the differences are differences of what is being covered and why, not of the word's basic meaning.
Most often it is a physical covering: water closing over the Egyptians, a cloud settling on the mountain, locusts blanketing the land, clothing laid over a body. From there it stretches naturally to hiding things that are not objects. To put a cloak over someone's nakedness is to clothe them; to put silence over a matter is to keep it secret; and in some of its most important uses, for God to cover sin is to put it out of sight so it is no longer held against the person.
The senses below sort these uses by what gets covered: a physical thing, a human body, a piece of information, or guilt before God. The word itself stays the same simple picture throughout, which is why English Bibles can render it "cover," "clothe," "conceal," and "forgive" for the one Hebrew verb.