Underun or Underrun: How To spell?
The word Underun is misspelled against Underrun, a verb meaning "To run or pass under; especially (Naut.), to pass along and under, as a cable, for the purpose of taking it in, or of examining it."
Underrun has double "rr" is mispronounced as "r"Remember double 'RR' in between the strings unde & un which should not be misspelled with single 'R'
Wrong Spelling:  unde-r-un  Correct Spelling:  unde-rr-un 
Check more misspelled words of Underrun to spell it correct.