stoor worm

noun1

1. •
   A giant sea serpent or sea dragon in Orcadian folklore, which had putrid breath, probably an Orkney version of Jörmungandr.

   • The Muckle Mester Stoor Worm was the father of all the terrible stoor worms that lived in the sea - huge sea monsters that destroyed ships and breathed poison over the land. — 2003