Толковый словарь английского языка - backbone

noun Date: 14th century spinal column, spine, something that resembles a ~: as, a chief mountain ridge, range, or system, the foundation or most substantial or sturdiest part of something, the longest chain of atoms or groups of atoms in a usually long molecule (as a polymer or protein), the primary high-speed hardware and transmission lines of a telecommunications network (as the Internet), firm and resolute character, spine 1c, ~d adjective