rumbling of the sea; oceanic noise; mistpouffer
Refers to the low, distant rumbling sound of the sea, often heard from the shore or inland. 'Mistpouffer' is a rare English term for a similar phenomenon.
At night, when I opened the window, I could hear the distant rumbling of the sea.
As a typhoon approaches, the rumbling of the sea grows louder.
Compound of 海 (umi, 'sea') and 鳴り (nari, 'rumbling sound'). The reading うみなり is a straightforward combination of the two elements.