The Collaborative International Dictionary of English v.0.48:

Overload \O`ver*load"\, v. t. [imp. & p. p. Overloaded; p. pr.
   & vb. n. Overloading.] [Cf. Overlade.]
   To load or fill to excess; to load too heavily.
   [1913 Webster]

The Free On-line Dictionary of Computing (17 December 2009):

overloading
ad-hoc polymorphism
operator overloading

    (Or "Operator overloading").  Use of a single
   symbol to represent operators with different argument types,
   e.g. "-", used either, as a monadic operator to negate an
   expression, or as a dyadic operator to return the difference
   between two expressions.  Another example is "+" used to add
   either integers or floating-point numbers.  Overloading is
   also known as ad-hoc polymorphism.

   User-defined operator overloading is provided by several
   modern programming languages, e.g. C++'s class system and
   the functional programming language Haskell's type
   classes.

   (1995-04-30)