[v] make secure underneath; "undergird the ship"
undergird
animate, assure, beef up, bolster, brace, brighten up, brisk, brisken, buck up, buttress, case harden, cheer, cheer up, chirk up, confirm, convalesce, embolden, encourage, enliven, exhilarate, fortify, fresh up, freshen, freshen up, gain strength, get bet