The current definition on the Knowledge Federation wiki is supplemented here with some additional explanations, customied to the Hermes project. 

Intuitively, knowledge federation is a social process whose purpose is to enable correct understanding and informed action. When capitalized, Knowledge Federation is the community of interest developing the theory and practice of knowledge federation.

What does 'correct understanding and informed action' practically mean? What do we need to do to get there?

Polyscopy — the current prototype of an informed approach to knowledge — is characterized by two keywords, perspective and gestalt. 

We say that we have a correct perspective of a subject or situation or phenomenon, when we have a correct understanding of the contributing factors and their relative importance, i.e. where nothing essential is distorted or missing. 

We say that we have an appropriate gestalt of a situation or issue when we have interpreted it correctly. Appropriate gestalt points to a course of action that is appropriate to a situation.  "Our car has a flat tire" is a textbook example of a gestalt. 

Obviously, correct perspective is a prerequisite for an appropriate gestalt. 

It is clear that acquiring a correct perspective depends on having access to, and listening to, all relevant sources of information and points of view. Knowledge federation can be understood as a social process that enables such listening.

It is as if we've been living in isolated countries (cultural islands, professional silos...) And then we began to create federations, where what the autonomy of our countries, the authenticity of our cultures and the identity of our people are still preserved, but where we are able to listen to each other and learn from each other, and live and act in syntony. 

Appropriate gestalt, however, does not automatically follow. Gestalts are often implicit in popular myths, they are power-related and subconsciously supported and induced. 

This is why knowledge federation operationalizes its goal by saying that a piece of information is properly federated and properly known only when it has enabled corresponding action.

A goal of Knowledge Federation is to evolve the ethics, science and art of knowledge federation in practice. Its key goal is to evolve the socio-technical mechanisms and processes that federate knowledge in key areas (science, democracy, governance, public informing, education...).