Hising or Hissing: How To spell?
The word Hising is misspelled against Hissing, a noun meaning "The act of emitting a hiss or hisses."
Hissing has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings hi & ing which should not be misspelled with single 'S'
Wrong Spelling:  hi-s-ing  Correct Spelling:  hi-ss-ing 
Find more wrongly spelled words of Hissing to spell it well.