Formal:
* Verbose: This is the most common and formal term for someone who uses more words than necessary.
* Prolix: Similar to verbose, but implying that the speaker is dull and tedious.
* Circumlocutory: Describes someone who uses roundabout or indirect language, avoiding the point.
* Plethoric: This word implies an excessive amount of words, like a flood of language.
Informal:
* Windbag: A very informal term for someone who talks excessively and often about unimportant things.
* Motormouth: Another informal term for someone who talks a lot and quickly.
* Loquacious: This is a more general term for someone who is talkative, but it doesn't necessarily imply that they use too many words.
The best word to use depends on the context and the level of formality you're aiming for.