substructure

sub·struc·ture  (sbstrkchr)

n.

1. The supporting part of a structure; the foundation.

2. The earth bank or bed supporting railroad tracks.

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sub·structur·al adj.

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substructure

Noun

1. a structure that forms a part of anything

2. a structure that forms a foundation or framework for a building

Thesaurus

Noun	1.	substructure - the basic structure or features of a system or organization infrastructure system - instrumentality that combines interrelated interacting artifacts designed to work as a coherent entity; "he bought a new stereo system"; "the system consists of a motor and a small computer" structure - the manner of construction of something and the arrangement of its parts; "artists must study the structure of the human body"; "the structure of the benzene molecule"
	2.	substructure - lowest support of a structure; "it was built on a base of solid rock"; "he stood at the foot of the tower" understructure, groundwork, base, foundation, fundament, foot bed - a foundation of earth or rock supporting a road or railroad track; "the track bed had washed away" raft foundation - a foundation (usually on soft ground) consisting of an extended layer of reinforced concrete structure, construction - a thing constructed; a complex entity constructed of many parts; "the structure consisted of a series of arches"; "she wore her hair in an amazing construction of whirls and ribbons" support - supporting structure that holds up or provides a foundation; "the statue stood on a marble support"