Undul or Undull: How To spell?
The word Undul is misspelled against Undull, a verb meaning "To remove the dullness of; to clear."
Undull has double 'll' in the end mispronounced as 'l'Remember double 'LL' appears in the end of this word which should not be misspelled with single 'L'
Wrong Spelling:  undu-l  Correct Spelling:  undu-ll 
Check more misspelled words of Undull to spell it correct.