Source : Webster's Revised Unabridged Dictionary (1913)

Tachina \Tach"i*na\, n.; pl. {Tachin[ae]}. [NL., fr. Gr. ?, for
   ? swift.] (Zo["o]l.)
   Any one of numerous species of Diptera belonging to {Tachina}
   and allied genera. Their larv[ae] are external parasites of
   other insects.