the world > movement > motion in specific manner > alternating or reciprocating motion > oscillation > oscillate [verb (transitive)] > wag (8)
To set in movement, cause to quiver or oscillate; to shake or stir by force. Obsolete.
To move lightly to and fro, to wag; esp. to wave a flag or other object to and fro in signalling; to signal in this way (intransitive, or transitive…