Princeton's WordNet

1. capital, capital letter, uppercase, upper-case letter, majuscule(adj)

   one of the large alphabetic characters used as the first letter in writing or printing proper names and sometimes for emphasis

   Antonyms:
   lowercase, minuscular, minuscule

   Synonyms:
   working capital, capital, chapiter, capital letter, upper-case letter, cap, majuscule, uppercase

2. majuscule(adj)

   of or relating to a style of writing characterized by somewhat rounded capital letters; 4th to 8th centuries

   Antonyms:
   lowercase, minuscular, minuscule

   Synonyms:
   capital, great

3. capital, great, majuscule(adj)

   uppercase

   Antonyms:
   minuscule, minuscular, lowercase

   Synonyms:
   slap-up, gravid, large(p), cracking, neat, majuscule, great(p), enceinte, swell, expectant, heavy(p), keen, nifty, with child(p), bang-up, smashing, not bad(p), corking, groovy, big(p), great, bully, dandy, peachy, outstanding, capital