shell has 16 distinct synonyms spread across 9 of its 18 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
ammunition consisting of a cylindrical metal casing containing an explosive charge and a projectile; fired from a large gun
the material that forms the hard outer covering of many animals
a rigid covering that envelops an object
“the satellite is covered with a smooth shell of ice”
a very light narrow racing boat
a metal sheathing of uniform thickness (such as the shield attached to an artillery piece to protect the gunners)
the hard largely calcareous covering of a mollusc or a brachiopod
Synonyms, antonyms and the broader and narrower relations for shell come from Princeton University’s WordNet. Full sources and licences.
fall out of the pod or husk
“The corn shelled”
hit the pitches of hard and regularly
“He shelled the pitcher for eight runs in the first inning”
look for and collect shells by the seashore
come out better in a competition, race, or conflict
“Agassi beat Becker in the tennis championship”