Physical necessity
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
A condition in which a person is absolutely compelled to act in a particular way by overwhelming superior force; as distingnished from moral necessity, which arises where there is a duty incumbent upon a rational being to perform, which he ought at the time to perform.
The Fortitude, 3 Sumn. 248, Fed. Cas. No. 4,953.