Definitions:
a large mollusc which has a tall spiral shell with a large aperture, living in tropical and subtropical seas.

a nucleus of a tritium atom, consisting of a proton and two neutrons.

a minor sea god usually represented as a man with a fish's tail and carrying a trident and shell-trumpet.

the largest satellite of neptune, the seventh closest to the planet and having a retrograde orbit and a thin nitrogen atmosphere, discovered in 1846 (diameter 2,700 km).