DCHP-1 Online
grayback 
n. Maritimes a large ocean wave.
- 1916 A seething grayback struck the dory and piled over the low gunnel.
- 1964 A languid "greyback" sea crawled under the dory's stern; the . . . craft yawed and slid . . . a little cloud of spray from the breaking crest of the following sea blew over.
- 1916 A seething grayback struck the dory and piled over the low gunnel.