Main Entry: back·bone

Pronunciation: \-ˈbōn, -ˌbōn\

Function: noun

Date: 14th century

1 : spinal column, spine
2 : something that resembles a backbone: as a : a chief mountain ridge, range, or system b : the foundation or most substantial or sturdiest part of something c : the longest chain of atoms or groups of atoms in a usually long molecule (as a polymer or protein) d : the primary high-speed hardware and transmission lines of a telecommunications network (as the Internet)
3 : firm and resolute character
4 : spine 1c

— back·boned \-ˌbōnd\ adjective