X in WordNet English dictionary

1. the cardinal number that is the sum of nine and one; the base of the decimal system
   ten  10  X  tenner  decade 
   
2. street names for methylenedioxymethamphetamine
   Adam  ecstasy  XTC  go  disco biscuit  cristal  X  hug drug 
   
3. the 24th letter of the Roman alphabet
   X  x  ex 
   
4. the 24th letter of the Roman alphabet
   X  x  ex