Definition of penny-rot in English:

penny-rot

noun

English Regional, Shropshire
  • Marsh pennywort, Hydrocotyle vulgaris, formerly supposed to cause liver rot in sheep.

Origin

Late 16th century; earliest use found in John Gerard (c1545–1612), herbalist. From penny + rot, after pennywort or penny-grass.

Pronunciation

penny-rot

/ˈpɛnɪrɒt/