Casus \Ca"sus\, n. [L.]
An event; an occurrence; an occasion; a combination of
circumstances; a case; an act of God. See the Note under
{Accident}.
[1913 Webster]
{Casus belli}, an event or combination of events which is a
cause war, or may be alleged as a justification of war.
{Casus fortuitus}, an accident against which due prudence
could not have provided. See {Act of God}, under {Act}.
{Casus omissus}, a case not provided for by the statute.
[1913 Webster]