The Collaborative International Dictionary of English v.0.48:

Vinegarroon \Vin`e*gar*roon"\, n. [Cf. Sp. vinagre vinegar.]
   A whip scorpion, esp. a large Mexican species (Thelyphonus
   giganteus) popularly supposed to be very venomous; -- from
   the odor that it emits when alarmed.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

vinegarroon
    n 1: large whip-scorpion of Mexico and southern United States
         that emits a vinegary odor when alarmed [syn:
         vinegarroon, Mastigoproctus giganteus]