Margining

1) In the stock market, buying or selling equity on credit.
(2) In the options market, the deposition of margin funds by options writers to cover the cost of buying or selling the underlying assets of their options. In the case of cash-settled options, they must deposit sufficient margin to cover the settlement of their positions. There are initial and variation margins. The initial margin is the deposit required on all open positions (long or short) to cover short-term price movements and is returned to members by the options exchange when the position is closed. The variation margin is the members' profits or losses, calculated daily from the marked-to-market-close value of their position (whereby contracts are revalued daily for the calculation of variation margin), and credited to or debited from their accounts
(3) similar to (2) with credit default derivatives a technique used when reducing or eliminating credit risk.