Definition of yarbles:
(n) :
(slang, vulgar) Testicles.
(n) :
(slang, mildly vulgar, figurative, uncountable) Courage, fortitude, or machismo.
(n) :
(slang, mildly vulgar, euphemistic, uncountable) Nonsense; something of unacceptably poor quality.
(n) :
(slang, mildly vulgar, euphemistic, uncountable) Information that is false or otherwise misleading.