Unlimited traffic

Some hosting companies advertise with "unlimited traffic" but what does it really mean?

When you read the user agreement of hosting offers with "unlimited traffic" there is almost allways a section saying that you are not allowed to missuse the account so that other hosing clients suffer. This means that you can't use the unlimited traffic to the unlimited. This offers is not good if you use alot of transfer per month as you cant say when you must pay extra for the transfer.