To restrain within boundaries; to limit; to confine
To consider (a function) as defined on a subset of its original domain.
The removal of a block or blockage.
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).