Wordnet 3.0
NOUN (2)
1. 
 an incomprehensible talk; 
2. 
 the difficult version of jump rope in which players jump over two ropes that are swung in a crisscross manner by two turners; 
WordNet (r) 3.0 (2006):
double Dutch
    n 1: an incomprehensible talk
    2: the difficult version of jump rope in which players jump over
       two ropes that are swung in a crisscross manner by two
       turners
Moby Thesaurus II by Grady Ward, 1.0:
20 Moby Thesaurus words for "double Dutch":
   Aesopian language, Babel, Greek, argot, babble, cant, cipher, code,
   cryptogram, garble, gibberish, gift of tongues, glossolalia,
   gobbledygook, jargon, jumble, noise, scramble, secret language,
   slang