*A combinator is a function that takes one or more arguments and produces a resu...

A combinator is a function that takes one or more arguments and produces a result without introducing anything new. In Ruby terms, we are talking about blocks, lambdas or methods that do not call anything except what has been passed in.

https://github.com/raganwald/homoiconic/blob/master/2008-11-...

Thanks for pointing out an important omission. Updated.