The Collaborative International Dictionary of English v.0.48:

Tachygraphy \Ta*chyg"ra*phy\, n. [Gr. tachy`s quick + -graphy:
   cf. F. tachygraphie.]
   The art or practice of rapid writing; shorthand writing;
   stenography. --I. Taylor (The Alphabet).
   [1913 Webster]

WordNet (r) 3.0 (2006):

tachygraphy
    n 1: a method of writing rapidly [syn: shorthand,
         stenography, tachygraphy]