look up any word, like the eiffel tower:
 
1.
to have muscles in your nuts
John took off his clothes and i saw his testicles... he had musticles
by AssAids69 September 29, 2012
 
2.
The word is directly interchangeable with the word muscle.

The plural is musticles.
Linda was as the gym, showing of her massive bicep musticles.
by in_a_ru5h May 09, 2010