Princeton's WordNet

1. couple, twosome, duo, duet(noun)

   a pair who associate with one another

   Synonyms:
   pas de deux, duad, duette, yoke, pair, duet, dyad, twosome, couplet, match, mates, brace, twain, couple, span, duo, distich

   Antonyms:
   decouple, uncouple

2. couple, mates, match(noun)

   a pair of people who live together

   Synonyms:
   lucifer, duad, equal, yoke, pair, duet, dyad, twosome, friction match, couplet, match, mates, brace, mate, compeer, twain, peer, couple, span, catch, duo, distich

   Antonyms:
   decouple, uncouple

3. couple(noun)

   a small indefinite number

   Synonyms:
   duo, span, twosome, mates, couplet, distich, duad, duet, dyad, pair, match, yoke, brace, twain

   Antonyms:
   decouple, uncouple

4. couple, pair, twosome, twain, brace, span, yoke, couplet, distich, duo, duet, dyad, duad(noun)

   two items of the same kind

   Synonyms:
   pas de deux, duad, bitstock, bracing, orthodontic braces, coupling, bridge, yoke, pair, gallus, duet, dyad, twosome, couplet, match, mates, suspender, braces, straddle, brace, twain, duette, couple, span, duo, distich

   Antonyms:
   decouple, uncouple

5. couple(verb)

   (physics) something joined by two equal and opposite forces that act along parallel lines

   Synonyms:
   duo, span, twosome, mates, couplet, distich, duad, duet, dyad, pair, match, yoke, brace, twain

   Antonyms:
   uncouple, decouple

6. match, mate, couple, pair, twin(verb)

   bring two objects, ideas, or people together

   Synonyms:
   fit, parallel, match, play off, touch, duplicate, gibe, equate, copulate, pair, couple on, checkmate, meet, agree, partner off, equal, check, pit, equalize, cope with, tally, rival, geminate, mate, pair off, couple, correspond, equalise, couple up, oppose, twin, jibe

   Antonyms:
   decouple, uncouple

7. couple, couple on, couple up(verb)

   link together

   Synonyms:
   partner off, pair, twin, couple, couple on, copulate, couple up, match, mate, pair off

   Antonyms:
   uncouple, decouple

8. pair, pair off, partner off, couple(verb)

   form a pair or pairs

   Synonyms:
   partner off, pair, twin, couple, couple on, copulate, match, geminate, mate, pair off, couple up

   Antonyms:
   decouple, uncouple

9. copulate, mate, pair, couple(verb)

   engage in sexual intercourse

   Synonyms:
   partner off, pair, checkmate, twin, couple, couple on, copulate, match, geminate, mate, pair off, couple up

   Antonyms:
   uncouple, decouple