Definition of "gis"

gis¹

noun
uncountable
1. (ornithology, slang) Alternative spelling of jizz
  Quotations
  Applied to birding, the gis approach involves a deemphasis of separate field marks in favor of the gestalt, the essence that tells us a dog is a dog […]
  1988 April 8, Jerry Sullivan, “Field & Street”, in Chicago Reader‎

gis²

contraction
1. Alternative form of gi's.