You searched for: “ondograph”
ondograph (s) (noun), ondographs (pl)
1. An instrument for graphically recording oscillatory variations, as in alternating currents.
2. Etymology: from French onde, "wave"; which came from Latin unda + -graph, "write, record".
This entry is located in the following units: grapho-, graph-, -graph, -graphy, -grapher, -graphia (page 60) undu-, und- (page 1)