understructure

Từ điển WordNet v3.1 - WordNet Dictionary

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
• Derivationally related forms:
basal (for: base)
• Hypernyms:
support
• Hyponyms:
bed, raft foundation
• Part Holonyms:
structure, construction