1. n. 
Multiply reflected seismic energy, or any event in seismic data that has incurred more than one reflection in its travel path. Depending on their time delay from the primary events with which they are associated, multiples are characterized as short-path or peg-leg, implying that they interfere with the primary reflection, or long-path, where they appear as separate events. Multiples from the water bottom (the interface of the base of water and the rock or sediment beneath it) and the air-water interface are common in marine seismic data, and are suppressed by seismic processing.
Synonyms: secondary reflection
See: abnormal events, acquisition, attenuate, autocorrelation, coherent noise, event, ghost, long-path multiple, noise, peg-leg multiple, primary reflection, short-path multiple, synthetic seismogram, vertical seismic profile