Chattering, n.
The act or habit of talking idly or rapidly, or of making inarticulate sounds; the sounds so made; noise made by the collision of the teeth; chatter.
Shades of meaning
Fernald has no entry of its own for chattering; he lists it under garrulous.
Where he writes about it:
To jabber is to utter a rapid succession of unintelligible sounds, generally more noisy than chattering. — from babble
Chattering signifies uttering rapid, noisy, and unintelligible, or scarcely intelligible, sounds, whether articulate words or such as resemble them; chattering is often used of vocal sounds that may be intelligible by themselves but are ill understood owing to confusion of many voices or other cause. — from garrulous
We speak of a chattering monkey or a chattering idiot, a talkative child, a talkative or loquacious woman, a garrulous old man, a verbose writer. — from garrulous