The Collaborative International Dictionary of English v.0.48:

Tenuate \Ten"u*ate\, v. t. [imp. & p. p. Tenuated; p. pr. &
   vb. n. Tenuating.] [L. tenuatus, p. p. of tenuare to make
   thin, fr. tenuis thin. See Tenuous.]
   To make thin; to attenuate. [R.]
   [1913 Webster]