definition of debt ratio ?

Answer 1

how much income you make ( net not gross ) to how much debt you owe
ideally the ratio is zero
but that is impossible as to some degree you are always in debt ( rent, utilities ect.. )
but anything beyond that will make things unecessarily tougher for you should you live beyond your means as many do

Answer 2

It is defined by your minimum payments to your debt to your gross income. Depends on what you are trying to do, a ratio of 50% or less, a mortgage lender will except.