If "reveal" means to make something known:
* Conceal: To hide or keep something secret.
* Hide: To put something out of sight.
* Suppress: To prevent something from being known or expressed.
* Obscure: To make something difficult to understand or see.
* Mask: To cover or disguise something.
If "reveal" means to show something:
* Cover: To put something over or in front of something else.
* Hide: To put something out of sight.
* Conceal: To hide something from view.
* Mask: To cover or disguise something.
* Obscure: To make something difficult to see.
If "reveal" means to uncover something:
* Cover: To put something over or in front of something else.
* Burry: To put something underground.
* Conceal: To hide something from view.
* Encase: To enclose something in a protective covering.
* Protect: To keep something safe from harm.
The best opposite of "reveal" will depend on the specific situation.