Assibilate :: Assibilate (v. t.) To make sibilant; to change to a sibilant.
Assibilation :: Assibilation (n.) Change of a non-sibilant letter to a sibilant, as of -tion to -shun, duke to ditch..
Sibilate :: Sibilate (v. t. & i.) To pronounce with a hissing sound, like that of the letter s; to mark with a character indicating such pronunciation..
Sibilation :: Sibilation (n.) Utterance with a hissing sound; also, the sound itself; a hiss..