margin call

from the GNU version of the Collaborative International Dictionary of English.

• noun (Stock market) A demand by a broker that a customer deposit enough to bring his margin up to the minimum requirement; -- caused by the decline in market prices of a security or commodity purchased on margin{5}.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun finance Request by a stockbroker or similar for the client to deposit more money in order to cover losses that have built up in open positions held on margin (rather than having been paid for in full).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a demand by a broker that a customer deposit enough to bring his margin up to the minimum requirement