Source : Webster's Revised Unabridged Dictionary (1913)

Ecthoreum \Ec`tho*re"um\, n.; pl. {Ecthorea}. [NL., fr. Gr. ? to
   leap out; ek out + ?, ?, to leap, dart.] (Zo["o]l.)
   The slender, hollow thread of a nettling cell or cnida. See
   {Nettling cell}. [Written also {ecthor[ae]um}.]