What do we really mean by "reproducible"?

[Santiago Vila]

Greetings.

Before I use this rationale more times in some discussions out there, I'd
like to be sure that there is a consensus.

What's the definition of reproducible? It is more like A or more like B?

A. Every time the package is attempted to build, the build succeeds,
and the same .deb are always created.

B. Every time the build is attempted and the builds succeeds, the
same .deb are always created.

In other words: It is ok to consider "always build ok" as a prerequisite
to consider a source package "reproducible"?

Thanks.