Definition of Adam's flannel in English:

Adam's flannel

noun

historical
  • The common mullein, Verbascum thapsus.

Origin

Early 19th century; earliest use found in William Carr (d. 1843). From the genitive of the name of Adam + flannel, apparently so called on account of its large soft woolly leaves.

Pronunciation:

Adam's flannel

/ˌadəmz ˈflanl/