'Underside' definitions:

Definition of 'underside'

From: WordNet
noun
The lower side of anything [syn: bottom, underside, undersurface]

Definition of 'Underside'

From: GCIDE
  • Underside \Un"der*side`\, n. The lower or lowest side of anything. --Paley. [1913 Webster]

Synonyms of 'underside'

From: Moby Thesaurus