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. See also
{pointy hat}, compare {patch pumpkin}.