I thought there was a discussion of this on this message board in the past, but I can't seem to find it.

Here is how the AACT (www.aact.org) theater dictionary defines it:

"Community theatre" generally refers to a nonprofit theatre company that serves a locality, relies heavily on volunteers, and does not use Equity (union) actors on a regular basis. Community theatres tend to be operated for local recreation, education, and commonly seek to obtain the patronage and production participation of the community as a whole."

There is really no solid definition that applies to all community theatre but this one is pretty good.

Dan