Both words refer to something horrifying and repellent—especially acts and images of violence and death, with no gore spared. Gruesome comes from a Germanic word for “shudder.” It suggests something graphic that evokes a visceral response. Macabre is a strong synonym for gruesome: a gruesome murder could also be described as macabre murder. However, macabre tends to describe things less tangible than gore, like an atmosphere, a mood, or an artistic or literary representation of something horrible. We can compare these typical uses: gruesome photos and gruesome video; macabre tale and macabre movie. Macabre is frequently paired with dark, bizarre, strange, and grotesque.
Both words refer to the act of misleading, tricking, or deceiving someone, usually for one’s own advantage or gain. Deception is the broader term, covering all ways of misleading people, from false appearances to lies: deception in advertising. Subterfuge is a category of deception that involves the use of cunning tricks or stratagems in order to get away with something. Subterfuge emphasizes the tricks themselves, particularly tricks that (like a smoke screen) hide or disguise what is actually going on: Going out would require subterfuge, so I set my music player to start one hour after I’d slipped out through my bedroom window. Politics, not espionage, is by far the most frequent context for subterfuge.
Both words can refer to a sudden spell of heightened emotion or activity, which for both words is an extension of a medical definition for a sudden attack or intensification of a disease. Paroxysm conveys a violent, serious spell of emotion or activity more consistently than fit, but both words are used of strong emotions: a fit of rage; paroxysms of anger, rage, laughter, grief. Fit can also be applied (without facetiousness) to the onset of less acute, intense states: a fit of inactivity; a fit of nostalgia. When eruptions of emotion and activity are attributed to whole populations or geopolitical entities, paroxysm is much more likely to be used: global paroxysms; a paroxysm of nationalism.