Definition of "slan"

The idea of a national government, covering all the slan race and nobody else, is seen in the many drives for a general fan organization.

1944, John Bristol Speer, “F - Fascism”, in Fancyclopedia‎

Here, at least once a month, the slans from Michigan gathered for sneak previews of forthcoming WARPS, to criticise some Rappian manuscript which Art was polishing for pro submission, or to talk about various subjects as fans are wont to do, and drink beer, pop, consume beans, dogs, chips, or eclairs.

1950 September, Charles Stuart Metchette, “Michigan Memories”, in Spacewarp‎, number 42, pages 72–77

Fen gather in clubhouses called slanshacks, "slan" meaning a biologically mutated superman.

1955, Arthur Koestler, The Trail of the Dinosaur and Other Essays, page 143