Backstor or Backstair: How To spell?

The word Backstor is misspelled against Backstair, an adjective meaning "Private; indirect; secret; intriguing; -- as if finding access by the back stairs."

Word contains consecutive vowels 'AI' in between alphabets backst & r is misspelled as 'O'
Wrong Spelling:  backst-o-r 
Correct Spelling:  backst-ai-r 
Find more incorrect spellings of Backstair to spell right way.

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