请看金融百科中对于margin call 的释义：

A broker's demand on an investor using margin to deposit additional money or securities so that the margin account is brought up to the minimum maintenance margin. Margin calls occur when a you account value depresses to a value calculated by the broker's particular formula. This is sometimes called a "fed call" or "maintenance call".

You would receive a margin call from a broker if one or more of the securities you had bought (with borrowed money) decreased in value past a certain point. You would be forced either to deposit more money in the account or to sell off some of your assets.

根据英文释义，margin call 就相当于中文的 追加保证金通知。

《英汉证券投资词典》对于该词的解释为：

追加保证金通知

亦为：补仓通知。

英语为：margin call；fed call；house call；house maintenance requirement；maintenance call。①证券公司向投资者发出的追加保证金或出售部分股票的通知。要求投资者在账户中增加资金或证券，以达到保证金账户的最低要求。保证金不足通常是由于市场变化，投资者的股票市值下跌。如果投资者不能满足追加保证金的要求，证券公司可强行平仓，补足保证金。保证金最低要求是美国联邦储备局制定的，所以也称为联储通知。

②期货交易过程中经纪商要求投资者追加保证金的通知。

【双语例句】

c. HKEx would manage the risk of AHFT through appropriate regular, ad-hoc and/or real time monitoring during the T+1 Session and via a new mandatory variation adjustment and margin call arrangement following the market open of each T Session and payable by 12:00 noon.

c. 香港交易所将通过适当的定期、随时和/或在T +1时段期间的实时监察，以管理收市后期货交易的风险，并通过新的强制变价调整及追加保证金要求在翌日T时段的中午12时前缴付。