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1.
A devoted fan of sci fi series 'Stargate SG-1' and/or 'Stargate Atlantis' and/or 'Stargate Universe'.

Biggest gateheads have joined online fandom, watch episodes on daily basis, and have SG marathon at least once a year. Long hiatus during new season can make 'em a little crazy.
Person #1: *keeps blabbering about Stargate and refuses to stop*
Person #2: Dude, you're a total gatehead.
Person #1: Why thank you.
by E01 January 24, 2010
 
2.
A completely devoted fan of the scifi series "Stargate SG-1/Atlantis"
If you watch (almost)every episode of the show as well as join discussion forums to talk to other gateheads.
by Kestra Scott October 30, 2006