The 乎乎 reduplication suffix turns adjectives into a softer, more vivid "sort of ___" feeling: 黑乎乎 (kind of dark/black), 热乎乎 (cozy and warm), 胖乎乎 (chubby). 晕乎乎 means "a bit dizzy" rather than full-on vertigo.
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Colloquial - fits casual speech, narration, or describing a tipsy/sleepy state. Often pairs with 头 (头晕乎乎的, head-spinny).
