Meaning

verb clear or remove an obstruction from

verb play the cards of (a suit) so that the last trick on which a hand can follow suit will be taken by a higher card in the hand of a partner who has the remaining cards of a combined holding

verb make (assets) available

originEtymology tree Proto-Indo-European *né Proto-Indo-European *n̥- Proto-Germanic *un- Proto-West Germanic *un- Old English un- Middle English un- English un- English block English unblock From un- + block.

Etymology from Wiktionary, CC BY-SA 3.0