The Collaborative International Dictionary of English v.0.48:

Cataplexy \Cat"a*plex`y\, n. [Gr. ? amazement: cf. Apoplexy.]
   (Med.)
   A morbid condition caused by an overwhelming shock or extreme
   fear and marked by rigidity of the muscles. --
   Cat`a*plec"tic, a.
   [Webster 1913 Suppl.]