Garrulous, voluble, loquacious, gasbag, and — in modern slang — diarrhea of the mouth. As you may have guessed, these descriptors generally refer to someone who is talkative. The specific definition for garrulous implies a wearisome loquacity about trivial matters. So, perhaps a friendly wave hello is all your neighbor wants. Here's an example of its usage from The Picture of Dorian Gray, by Oscar Wilde: [The housekeeper] lingered for a few moments, and was garrulous over some detail of the household. [Dorian] sighed and told her to manage things as she thought best. She left the room, wreathed in smiles.