Definitions:
the hard protective outer case of a mollusc or crustacean

an explosive artillery projectile or bomb

something resembling or likened to a shell because of its shape or its function as an outer case

the metal framework of a vehicle body.

a light racing boat.

an inner or roughly made coffin.

the hand guard of a sword.

each of a set of orbitals around the nucleus of an atom, occupied or able to be occupied by electrons of similar energies

bombard with shells

remove the shell or pod from (a nut or seed)