'Substructure' definitions:

Definition of 'substructure'

From: WordNet
noun
The basic structure or features of a system or organization [syn: infrastructure, substructure]
noun
Lowest support of a structure; "it was built on a base of solid rock"; "he stood at the foot of the tower" [syn: foundation, base, fundament, foot, groundwork, substructure, understructure]

Definition of 'Substructure'

From: GCIDE
  • Substructure \Sub*struc"ture\, n. [Pref. sub- + structure.]
  • 1. (Arch.) Same as Substruction. [1913 Webster]
  • 2. An under structure; a foundation; groundwork. [1913 Webster]