Words at Play : Top 10 Favorite British Words, Vol. 1
Definition:
to talk in a low inarticulate way: mutter
Example:
"Tell me about it. I was chuntering on last night about *padded* training bras." michlan on Twitter, April 13, 2011
About the word:
Chunter is sometimes used as a synonym of "complain." The word is probably imitative in origin: when people are chuntering, it sounds a bit like they're saying "chunter chunter." (Mutter is also imitative.)