to sell one's assets for cash and to determine one's liabilities, typically in order to pay off a debt and/or to conclude the affairs of a firm/company;
e.g. The company was forced to liquidate its merchandise at incredibly low prices to cover its debts.
(verb)
in informal usage, to eliminate someone or something, usually violently, for example by killing them;
e.g. They were sent to liquidate the villain before he could do anything else.