English

Noun

megafan ‎(plural megafans)

1. (geology) A very large mass of clastic sediment deposited by a laterally mobile river system that fans out from the outlet from a large mountainous drainage network.
   • 2011, James S. Albert, ‎Roberto E. Reis, Historical Biogeography of Neotropical Freshwater Fishes, ISBN 0520948505, page 197:

     The dynamics of river systems in megafan environments may strongly influence the fragmentation and reconnection of riverine habitats, and therefore by implication, the diversification and distribution of freshwater organisms.

2. (informal) An obsessively enthusiastic fan.
   • 2007 October 4, Melena Ryzik, “Radiohead Fans, Guided by Conscience (and Budget)”, in New York Times:

     Nathan Kaufman, 25, another Radiohead megafan, said of the plan, “I got geeked about it immediately.”

Synonyms

• (extreme fan): stan, superfan, trufan, uberfan