This term is frequently used in courts of equity and by writers on equity jurisprudence. It signifies the act by which a party who is entering into a contract is taken unawares, by which sudden confusion or perplexity is created, which renders it proper that a court of equity should relieve the party so surprised. The word surprise is a technical expression, and nearly synonymous with fraud. It is sometimes, used in this sense when it is deemed presumptive of, or approaching to fraud.
In practice, by surprise is understood that situation in which a party is placed, without any default of his own, which will be, injurious to his interest. The courts always do everything in their power to relieve a party from the effects of a surprise, when he has been diligent in endeavouring to avoid it.