A equatorial Kelvin wave is a type of oceanic wave that may play an important role in the ENSO cycle. See:
Quoting:
The equatorial zone essentially acts as a waveguide, causing disturbances to be trapped in the vicinity of the equator, and the equatorial Kelvin wave illustrates this fact because the equator acts analogously to a topographic boundary for both the Northern and Southern Hemispheres, making this wave very similar to the coastally-trapped Kelvin wave.
Compare also oceanic Rossby wave.