What's a seminar?

Years ago, Huk Planas asked a class what a seminar was. Nobody seemed to know the answer. (I'm sure someone did, but you know how it goes in a group - nobody wants to look stupid in front of anyone.) He said it meant "to plant a seed". Good enough.
Below is the dictionary definition.

sem·i·nar

sem·i·nar [sémmə nr]
(plural sem·i·nars)
n
1. meeting on specialized subject: a single session or short, often one-day meeting devoted to presentations on and discussion of a particular topic, usually at an advanced or professional level
2. specialized educational class: a course of specialized graduate or undergraduate study under faculty supervision, in which ideas, approaches, and advances are regularly shared among participants
3. meeting of students and academic supervisor: a meeting of university or college students for study or discussion with an academic supervisor, or the group that participates in it


[Late 19th century. Via German , “advanced class,” from Latin seminarium “seed plot, breeding ground,” ultimately from the stem semin- (see seminal).]
Encarta ® World English Dictionary © & (P) 1998-2004 Microsoft Corporation. All rights reserved.

I think his definition fit. And he did go on to add the part about students meeting with a professor. He also added that it was advanced material not normally covered in regular classes. And that's what I like to keep in mind when I do seminars.
I want everyone, regardless of rank (myself included) to go home with more than they came with. It's sometimes very difficult to structure a lesson plan with that as the goal.
All too often, I believe, guest instructors come in with no real lesson plan in mind or with one plan they do over and over. I think that's a bit of a disservice.
I get invited to schools all over and I often tailor-make the lesson plan for their group. Time consuming? Yes. Worth the effort? Definitely.
My Professional Development Seminars go beyond the structure that most seminars use. The planning and creation of unique materials is a key. I am proud of the product and the result. And there's a lot of people out there who seem to agree.
Attending seminars is a part of your time and money budget for your martial art education. Make sure they're worth it.
What do you think of most seminar structures?