The writer for "Court Martial" was using a term that was in common use in the 1960's. I illustrated what this term meant, for it's possible that this is what the writer envisioned when he wrote that episode.
Per Balance of Terror, both sides in the Earth-Romulan War employed atomic weapons. The ships of the Romulan navy in the 2260s retained the warheads of these weapons for self-destruction. And, it is demonstrated in the episode, that a single warhead could threaten a Federation starship. The Enterprise
destroyed the warhead, resulting in minor radiation burns for crew members who were working in the ship's outer areas. According to McCoy, the injuries could have been far worse if the warhead hit the ship.