Definition of rattlesnake fern in English:

rattlesnake fern

noun

  • An unusually tall moonwort of Eurasia and North America, Botrychium virginianum, with a triangular, ternately compound sterile blade from which a fertile frond emerges, thought to resemble the tail of a rattlesnake.

Origin

Early 19th century; earliest use found in Frederick Pursh (1774–1820).