Source : Webster's Revised Unabridged Dictionary (1913)

Oast \Oast\ ([=o]st), n. [OE. ost, AS. [=a]st; cf. Gr. a'i^qos
   burning heat.]
   A kiln to dry hops or malt; a cockle. --Mortimer.

Source : WordNet®

oast
     n : a kiln for drying hops