#1 sibilate v. pronounce with an initial sibilant. wn
#2 sibilate v. utter a sibilant. wn
#3 sibilate v. [hiss, sizz, siss] express or utter with a hiss. wn
#4 sibilate v. [hiss, siss, sizz] make a sharp hissing sound, as if to show disapproval. wn
vizzz