A person who is good at and loves playing an instrument in an orchestra (usually a school or youth orchestra). Usually these people are friends with other musically inclined people (band geeks, choir queers). Orch dorks are also usually very passionate about and familiar with various pieces of classical music. They are always talking about orchestra, bringing up jokes and situations from orchestra, and looking forward to orchestra. They often have a very strong opinion about their conductor. They're capable of being sophisticated people, but they choose not to be.
We're such orch dorks. We made up an interpretive dance to the piece we're playing.