"Syntactic sugar" is a term coined by Peter J. Landin for additions to the syntax of a language that do not affect its expressiveness but make it "sweeter" for humans to use. Syntactic sugar gives the programmer an alternative way of coding that is more succinct or more like some familiar notation. It does not affect the expressiveness of the formalism (compare chrome).
Syntactic sugar can be easily translated ("desugared") to produce a program in some simpler "core" syntax. E.g. C's a[i] notation is syntactic sugar for *(a + i). In a (curried) functional language, all operators are really functions and the use of infix notation x+y is syntactic sugar for function application (+) x y.
Alan Perlis once quipped, "Syntactic sugar causes cancer of the semicolon."
Compare candygrammar, syntactic salt.