Relating to or being deposits, especially near the mouth of a river, formed by the combined action of river and sea.
[Latin fluvius, river; see fluvial + marine.]
1. (Geological Science) (of deposits) formed by joint action of the sea and a river or stream
2. (Zoology) (esp of fish) able to live in both rivers and the sea
[C19: fluvio-, from Latin fluvius river + marine]