Describing organisms that swim or drift in a sea or a lake, as distinct from those that live on the bottom (seebenthos). Pelagic organisms are divided into plankton and nekton.
Geology and Earth Sciences
In marine ecology, applied to the organisms that inhabit open water, i.e. plankton, nekton, and neuston (although neuston are fairly unimportant in such environments).
Geography
Of marine life, belonging to the upper layers of the sea.