torpedo has 26 distinct synonyms spread across 3 of its 8 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.
a professional killer who uses a gun
a large sandwich made of a long crusty roll split lengthwise and filled with meats and cheese (and tomato and onion and lettuce and condiments); different names are used in different sections of the United States
an explosive device that is set off in an oil well (or a gas well) to start or to increase the flow of oil (or gas)
a small firework that consists of a percussion cap and some gravel wrapped in paper; explodes when thrown forcefully against a hard surface
a small explosive device that is placed on a railroad track and fires when a train runs over it; the sound of the explosion warns the engineer of danger ahead
armament consisting of a long cylindrical self-propelled underwater projectile that detonates on contact with a target
any sluggish bottom-dwelling ray of the order Torpediniformes having a rounded body and electric organs on each side of the head capable of emitting strong electric discharges
Synonyms, antonyms and the broader and narrower relations for torpedo come from Princeton University’s WordNet. Full sources and licences.