We don't have synonyms for half shell yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are hard shell, half cell and harp shell.
(n) :
(of food, especially with "on the") Either half of a clamshell especially when used to serve individual portions of spiced, minced, breaded, baked clams.
(n) :
(physics, figuratively) Any half of a roughly spherical-like object; any dome-shaped object.
(adj) :
(rare, colloquial, especially with "on the") Inexpensive; not overpriced.
(n) :
(of food, especially with "on the") Either half of a clamshell especially when used to serve individual portions of spiced, minced, breaded, baked clams.
(n) :
(physics, figuratively) Any half of a roughly spherical-like object; any dome-shaped object.
(adj) :
(rare, colloquial, especially with "on the") Inexpensive; not overpriced.