Serpiginous means possessing an undulating border. Medically it was originally, and still is commonly, applied to skin lesions. However radiology adopted it as a useful descriptive word for various imaging appearances e.g. calclfied vessels 2.
History and etymology
It derives from the Latin word serpigo, itself derived from sepere, meaning "to creep". The English word 'serpent' derives from the same Latin root 1.