The Collaborative International Dictionary of English v.0.48:

Krummhorn \Krumm"horn`\, Krumhorn \Krum"horn`\
   (kr[=oo]m"h[^o]rn`), n. [G. krummhorn cornet; krumm crooked +
   horn horn.] (Mus.)
   (a) A reed instrument of music of the cornet kind, now
       obsolete (see Cornet, 1, a.).
   (b) A reed stop in the organ; -- sometimes called cremona.
       [1913 Webster]

WordNet (r) 3.0 (2006):

krummhorn
    n 1: a Renaissance woodwind with a double reed and a curving
         tube (crooked horn) [syn: krummhorn, crumhorn,
         cromorne]