The Free On-line Dictionary of Computing (30 December 2018):

implicit type conversion
coercion

    (Or "coercion") The abilty of some compilers
   to automatically insert type conversion functions where an
   expression of one type is used in a context where another type
   is expected.

   A common example is coercion of integers to reals so that
   an expression like sin(1) is compiled as sin(integerToReal(1))
   where sin is of type Real -> Real.

   A coercion is usually performed automatically by the compiler
   whereas a cast is an explicit type conversion inserted by
   the programmer.

   See also subtype.

   (1997-07-28)