Whats a flight engineer ?
A flight deck crew member who occupies the seat behind the pilots...
I believe it was a facetious question/observation/comment. Sort of like, "what's a phonograph?" or "what's a soft field takeoff?"
Damned young turks and their youth...

Dave
PS Actually, I feel as though the answer to "What's a flight engineer" might present possibilities for an ongoing thread on Jetblast. For instance, I believe that a qualified South Park answer might be, "about three-fitty." However, I'm thinking that Drapes would add much to my meager attempt...