Chatterbox

Sven was so verbose that his friends resorted to calling him a chatterbox.

She is a chatterbox.

She is, in brief, a chatterbox.

That boy is a chatterbox.

Tom is a chatterbox.

Mary is a chatterbox.

She's a chatterbox.

The chatterbox can explain it well, but at the end of the day he has said nothing meaningful.

'I never can get a word in edgeways when I'm with you,' she returned. 'You're such a chatterbox.'

She's a proper chatterbox, whereas her husband is downright uncommunicative.

[S]he [Edwina, mother of Tennessee Williams] was indeed Amanda [Wingfield, character in Williams' play The Glass Menagerie] in the flesh: a doughty chatterbox from Ohio who adopted the manner of a Southern belle and eschewed both drink and sex to the greatest extent possible.