One shell of a bivalve: as, oysters served on the half-shell (that is, with the upper shell removed, and the oyster served raw on the lower one).(noun)
The Century Dictionary (Public Domain)
Use "half-shell" in a sentence
"This was partly because the oysters, which arrived in Puget Sound in the 1920s, require concerted husbandry to produce a worthy tasting half-shell oyster, and partly because they look a little off-putting, what with those black or brown filtering mantles around their rims."
"Patrick McMullan Christy Turlington with Corey and Michelle Jassem Guests nibbled on treats from host Tom Colicchio's restaurants, including duck prosciutto, scallops on the half-shell, stuffed zucchini blossoms and a variety of tomatoes."
"The experience you're paying for is the whole clam, its own half-shell stuffed with fresh, seasoned bread crumbs, then placed under a burning hot broiler so as to render it browned and just crisp enough."