Definition of field slug in English:

field slug

noun

  • Any of various terrestrial slugs; especially (more fully "grey field slug") Deroceras reticulatum (family Agriolimacidae), native to Europe and widely introduced in North America and elsewhere, which is an important pest of crops and garden plants.

Origin

Early 19th century; earliest use found in Robert John Thornton (1768–1837), physician and writer on botany.