m in WordNet English dictionary

1. the 13th letter of the Roman alphabet
   M  m 
   
2. the 13th letter of the Roman alphabet
   M  m 
   
3. the basic unit of length adopted under the Systeme International d'Unites (approximately 1.094 yards)
   meter  metre  m 
   

1. denoting a quantity consisting of 1,000 items or units
   thousand  one thousand  1000  m  k