Deful or Defail: How To spell?

The word Deful is misspelled against Defail, a verb meaning "To cause to fail."

Word contains consecutive vowels 'AI' in between alphabets def & l is misspelled as 'U'
Wrong Spelling: def-u-l
Correct Spelling: def-ai-l
Check more misspelled words of Defail to spell it correct.