The Collaborative International Dictionary of English v.0.48:

Sextuple \Sex"tu*ple\, a. [Formed (in imitation of quadruple)
   fr. L. sextus sixth: cf. F. sextuple.]
   1. Six times as much; sixfold.
      [1913 Webster]

   2. (Mus.) Divisible by six; having six beats; as, sixtuple
      measure.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sextuple
    adj 1: having six units or components [syn: sextuple,
           sixfold, six-fold]