To talk for a long time about things that are not important. (Cambridge Dictionary)
If animals chatter, they make quick, repeated noises. (Cambridge Dictionary)
If you chatter, you talk quickly and continuously, usually about things which are not important. (Collins Dictionary)
To utter rapid short sounds suggestive of language but inarticulate and indistinct. (Merriam – Webster)
Talk informally about unimportant matters. (Oxford Dictionaries)
Blab and Chatter. Thesaurus plus.
Why Do Cats Chatter?