Can't get your point across? Maybe you just need to speak more clearly or articulate your thoughts better — in short, enunciate.
Good enunciation is similar to pronunciation, but describes more specifically how clearly someone expresses themselves. The word enunciate is related to the Latin words for both "announce" and "messenger." So most likely those ancient Romans who created the word wanted a messenger who could announce things without mumbling, grumbling, and rambling.