Estuary

Part of speech: noun (n.)

1. A place where water boils up; a spring that wells forth. [Obs.] Boyle.

2. A passage, as the mouth of a river or lake, where the tide meets the current; an arm of the sea; a frith. it to the sea was often by long and wide estuaries. Dana.

Part of speech: adjective (a.)

Belonging to, or formed in, an estuary; as, estuary strata. Lyell.