The Collaborative International Dictionary of English v.0.48:

Monocrotism \Mo*noc"ro*tism\, n. [Gr. mo`nos alone + ? a
   beating.] (Physiol.)
   That condition of the pulse in which the pulse curve or
   sphygmogram shows but a single crest, the dicrotic elevation
   entirely disappearing.
   [1913 Webster]