NOD (3)

Nod (?), n. 1. 1. A dropping or bending forward of the upper part or top of anything.
Like a drunken sailor on a mast, Ready with every nod to tumble down. Shak. 2. 2. A quick or slight downward or forward motion of the head, in assent, in familiar salutation, in drowsiness, or in giving a signal, or a command.
A look or a nod only ought to correct them when they do amiss. Locke. Nations obey my word and wait my nod. Prior. The land of Nod, sleep.