Dictionary of difficult words. 2015.
siffilate — sif·fi·late … English syllables
siffilate — To talk in a whisper … Grandiloquent dictionary
siffilate — ˈsifəˌlāt verb ( ed/ ing/ s) Etymology: modification (influenced by sibilate) of French siffler to whistle, from Middle French : whisper … Useful english dictionary