The legal definition of an "Act of God" has been given in the case of Nugent Vs. Smith (1876) 1 CPD 423 where it has been held that a loss occasioned by an Act of God is a loss arising from and occasioned by the agency of nature which cannot be guarded against by the ordinary exertions of human skill and prudence so as to prevent its effect. An "Act of God" was always a common law exception. It was a metaphorical phrase (like "fate") with a religious origin used to describe those events which involved no human agency and which it was not realistically possible for a human to guard against. 

( HRC Shipping Ltd. Vs. MV X-Press Manaslu, MV X-Press Resolve & others, 2006, 35 CLC (HCD) [4749] )