tat·tle 
(t
ăt
l)
v. tat·tled, tat·tling, tat·tles
v.intr.1. To reveal the plans or activities of another, especially ones that are secret or improper: tattled on his sister when she snuck out; tattled to his parents about what his sister did.
2. To chatter; prate.
v.tr. To reveal (something about someone) to another, as through gossiping.
n.1. Idle talk; chatter; prattle.
2. A tattletale.
[Middle English tatelen, to stammer, probably from Middle Dutch, of imitative origin.]
tattling·ly adv.