wizard hat n.
[also, after Terry Pratchett, `pointy hat'] Notional headgear
worn by whoever is the wizard in a
particular context. The implication is that it's a transferable
role. "Talk to Alice, she's wearing the TCP/IP wizard hat while
Bob is on vacation." This metaphor is sufficiently live that one
may actually see hackers miming the act of putting on, taking
off, or transferring a phantom hat. Compare patch pumpkin.