to cover something, so as to make it impossible to see.
to prevent from entering or penetrating.
to prevent (a thought) from entering one's mind.
to begin to reduce to shape; to mark out roughly; to lay out.
To remove or clear a block or obstruction from.
In whist, to throw away a high card so as not to interrupt one's partner's long suit.
To free or make available.
To enable communication again, via telephone, instant messaging, etc., with (somebody previously blocked).
The removal of a block or blockage.