The Collaborative International Dictionary of English v.0.48:

Hornito \Hor*ni"to\, n. [A dim. fr. Sp. horno oven, L. furnus.
   See Furnace.] (Geol.)
   A low, oven-shaped mound, common in volcanic regions, and
   emitting smoke and vapors from its sides and summit.
   --Humboldt.
   [1913 Webster]