脊梁 (jǐliáng) literally means the spinal column (backbone); figuratively, it means 'backbone, mainstay'—the central support of a group or nation. Compared to 支柱 (zhīzhù, a structural pillar) and 骨干 (gǔgàn, a core organizational member), 脊梁 emphasizes the fundamental supporting role. 栋梁 (dòngliáng) is a literary synonym for 'pillar of the nation'.