The Collaborative International Dictionary of English v.0.48:

popcorn \pop"corn`\, pop corn \pop" corn`\, n.
   See pop corn under pop, n..
   [PJC]

WordNet (r) 3.0 (2006):

popcorn
    n 1: corn having small ears and kernels that burst when exposed
         to dry heat [syn: popcorn, Zea mays everta]
    2: small kernels of corn exploded by heat

The Free On-line Dictionary of Computing (30 December 2018):

POPCORN

   AI system built on POP-2.  "The POPCORN Reference Manual", S.
   Hardy, Essex U, Colchester, 1973.