C programmer abbreviation for "variable arguments",
referring to a function that accepts parameters this way,
as opposed to a more normal function which is always called with a fixed number of arguments.
The classic example of a varargs function is printf.
Dennis Ritchie is said to have admitted that one of the more glaring discrepancies in early C was that "varargs functions are not permitted, yet printf exists."
Varargs functions were first implemented using black magic,
then with a semistandard header called <varargs.h>,
and were finally condoned and standardized in the ANSI/ISO C Standard, which described a new header, <stdarg.h>, for implementing them.