I'm now a member of my department's colloquium committee. Our task is to make a great colloquium series. I thought that the first step would be to come up with an appropriate definition of "Mathematics Colloquium." Standard dictionaries are not too much help:
Colloquium: n. 1. A usually academic meeting at which specialists deliver addresses on a topic or related topics and then answer questions relating to them. 2. A conference at which scholars or other experts present papers on, analyze, and discuss a specific topic.
So here's my question: What is the ideal definition of a mathematics colloquium? Of course I know a bunch of things that make for bad colloquium talks, so I'm interested in knowing the definition of a good or great mathematics colloquium.