The Free On-line Dictionary of Computing (18 March 2015):
An argument passing convention where the
address of an argument variable is passed to a function or
procedure, as opposed to passing the value of the argument
expression. Execution of the function or procedure may have
side-effects on the actual argument as seen by the caller.
The C language's "&" (address of) and "*" (dereference)
operators allow the programmer to code explicit
call-by-reference. Other languages provide special syntax to
declare reference arguments (e.g. ALGOL 60).
See also call-by-name, call-by-value,