The Ohio Learning Network Definition
A group of colleagues that come together and commit to work collaboratively; provide information, ideas, feedback, reflection, and support for their colleagues; and continuously assess and reassess community goals and activities, share expertise and resources, experience personal and collective growth, and increase the capacity to use learning technologies effectively.
See also: An Introduction and History to the OLN Learning Communities Initiative

OLN Learning Communities Defined the Concept
A learning community is a voluntary (often cross-disciplinary) group of committed members who are risk-takers, contributors and who express trust in a team effort to explore learning. This joint effort is most successful when it has institutional and colleague support. Members collaborate around a common goal, solve problems and launch initiatives that often involve complex issues. They explore these topics in a non-threatening environment that lacks politics but has a commitment to students. Outcomes evolve out of an ongoing process that includes research, discussion and reflection. The outcomes may vary perhaps leading to "floating outcomes".

Communities of Practice Definition
"Communities of Practice" is a phrase coined by researchers who studied the ways in which people naturally work and play together. In essence, communities of practice are groups of people who share similar goals and interests. In pursuit of these goals and interests, they employ common practices, work with the same tools and express themselves in a common language. Through such common activity, they come to hold similar beliefs and value systems.
See also: The Community Intelligence Lab

Communities of Practice Defined by Etienee Wenger
Communities of practice are groups of people who share a concern or a passion for something they do and learn how to do it better as they interact regularly. A community of practice has an identity defined by a shared domain of interest. Membership therefore implies a commitment to the domain, and therefore a shared competence that distinguishes members from other people. In pursuing their interest in their domain, members engage in joint activities and discussions, help each other, and share information. They build relationships that enable them to learn from each other. Members of a community of practice are practitioners. They develop a shared repertoire of resources: experiences, stories, tools, ways of addressing recurring problems—in short a shared practice. This takes time and sustained interaction.
See also: A brief introduction to Communities of Practice by Etienee Wenger

Miami University Definition
A faculty learning community (FLC) is a group of trans-disciplinary faculty, graduate students and professional staff group of size 6-15 or more (8 to 12 is the recommended size) engaging in an active, collaborative, yearlong program with a curriculum about enhancing teaching and learning and with frequent seminars and activities that provide learning, development, transdisciplinarity, the scholarship of teaching and learning, and community building.
See also: Miami University's 30 components of a FLC