• (n.) A tracing or chart showing the phenomena attendant on thunderstorms. • (n.) An instrument for making such tracings, as a recording brontometer.
Bron'to·graph noun [ Greek ... thunder + -graph .] (Meteor.) (a) A tracing or chart showing the phenomena attendant on thunderstorms. (b) An instrument for making such tracings, as a recording brontometer. 
brontography, brontograph, brontographic An instrument for recording the phenomena associated with thunderstorms.brontograph A recording brontometer; also, a chart of thunder phenomena recorded by that instrument.