[common] Said of a capability of a programming language or hardware
that is available by its design without needing cleverness to implement:
In APL, we get the matrix operations for free.
And
owing to the way revisions are stored in this system, you get revision
trees for free.
The term usually refers to a serendipitous feature
of doing things a certain way (compare big win), but
it may refer to an intentional but secondary feature.