assibilate

from WordNet (r) 3.0 (2006)

assibilate
    v 1: insert a sibilant sound before or after (another sound)
    2: change into a sibilant; "In the syllable /si/, the /s/
       sibilates in Japanese"

from The Collaborative International Dictionary of English v.0.48

Assibilate \As*sib"i*late\, v. t. [L. assibilatus, p. p. of
   assibilare to hiss out; ad + sibilare to hiss.]
   To make sibilant; to change to a sibilant. --J. Peile.
   [1913 Webster]

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