Not all boredom is created equal. Sometimes it’s a fleeting response to circumstance, sometimes it’s a symptom of your ongoing existential crisis.
The word ennui tends toward the latter. Defined as “a feeling of utter weariness and discontent resulting from satiety or a lack of interest,” it comes from the Old French word enui, meaning “displeasure or annoyance.” (In fact, that same Old French root also gives us the word annoy.)
Its peak usage was in Victorian and Romantic literature to express a profound sense of listlessness, as well as feelings of emptiness and alienation. These days, ennui is used in a similar way, describing the kind of "what-does-it-all-mean" boredom that people feel when they can't even be satisfied with satisfaction.