Fully developed sea
From AMS Glossary
fully developed sea
(Also called fully arisen sea.) A sea for which the input of energy to the waves from the local wind is in balance with the transfer of energy among the different wave components, and with the dissipation of energy by wave breaking.
Usually this is taken to mean that the sea state is independent of the distance (fetch) over which the wind blows and the time (duration) for which it has been blowing. Some of the wave components of the energy spectrum may not have their maximum amount of spectral energy in a fully developed sea, as an "overshoot" tends to occur during the process of wave growth.