ˈgrils also -lts noun
( plural grilse also grilses )
Etymology: Middle English grills, grilles
: a young mature Atlantic salmon returning from the sea to spawn for the first time when between 3 and 3 1/2 years of age, being chiefly a small male of 4 to 12 pounds, and being very vigorous and active when compared with older fish ; also : any of various other salmon at a stage of development comparable to that of the Atlantic salmon grilse