›[T]to reduce or remove a large amount of something: drain sth from sthThe government is enforcing a deal that allows it to drain billions from miners' pension schemes.drain reserves/resourcesThey took on work that was not profitable, draining cash resources.
›[I]to disappear gradually: How can we make sure business does not drain out of the country?The riches lured in too much competition and profits are now beginning to drain away.