1. an additional positive that makes something good even better
that's just the icing on the cake
In a literal sense, icing is an inessential sugary coating applied to a cake, often for decorative purposes. Figuratively, therefore, this expression is generally used in a positive sense to refer to an already good situation being made even better by the addition of something. Occasionally, however, 'icing on the cake' can be used in a sarcastic manner in relation to something negative. The term is common in both a social and professional environment and is similar to the phrase 'cherry on top.'