Humorous:
* Malapropist: This refers to someone who uses incorrect words that sound similar to the correct ones, creating a humorous effect.
* Wordsmith (in a satirical sense): This implies someone who thinks they're good with language but actually misuses words.
* Sesquipedalian: This simply means someone who uses long words, regardless of whether they're used correctly.
More critical:
* Pretentious: This suggests someone is trying to impress with their vocabulary, but is actually using it poorly.
* Ignorant: This is a harsher term, implying the person simply doesn't know the meaning of the words they're using.
* Pedantic: This describes someone who focuses on minor details of language, often in a way that is annoying or distracting.
Neutral:
* Misuser of words: This is a straightforward description without judgment.
* Someone with a poor vocabulary: This emphasizes the lack of knowledge, not the intention.
The best term to use will depend on the context and your perspective on the person's word usage.