Thumping sound when coasting

[homegr0wn]

I have a 1999 civic and there is a thumping sound that I can almost feel in the floorboards when I am coasting. It doesn't happen only in turns and it goes away when I accelerate or brake. I've seen other people post that they've had the same symptoms, but I've never seen an answer posted as to what the problem may be. Any ideas?

Thanks!