Disposable income
Income not reasonably necessary for the maintenance or support of the debtor or dependents. If the debtor operates a business, disposable income is defined as those amounts over and above what is necessary for the payment of ordinary operating expenses.
Additional Sources
Answers.com
The amount of after-tax income that is available to divide between spending and personal savings.
Encyclopedia Britannica
That portion of an individual’s income over which the recipient has complete discretion. An accurate general definition of income is not easy to provide. Income includes wages and salaries, interest and dividend payments from financial assets, and rents and net profits from businesses. Capital gains on real or financial assets should also be counted as income in most cases, at least insofar as they increase spending power. Such gains may even be counted where the asset is not actually sold and the increase in spending power is not exercised. In addition, receipts not in the form of cash—income in kind—may be included.
Disposable income involves a further adjustment to exclude obligatory payments in the form of direct taxes, compulsory payments to social-insurance schemes, and the like and to include simple transfers from other persons, institutions, or the government such as social-security benefits, pensions, and alimony. In some cases the boundary between voluntary and obligatory payments is blurred so that the meaning of disposable income becomes ambiguous. Also, a distinction may have to be made between transfer income to which a person is entitled and that which is actually received.
By convention, indirect taxes, such as value-added and other sales taxes, payroll taxes, and employers’ contributions to social insurance, are not deducted from the computation of disposable income. Although these clearly reduce private spending power generally, it is difficult to attribute their incidence to specific persons and families. It should also be noted that when members of families or other units share in a “pool” of income, there may be a substantial divergence between a person’s nominal disposable income (as recorded, for example, on his paycheck) and his actual discretionary spending power. Thus, a person who appears in official statistics as having a very low after-tax income may in fact be a part-time worker contributing to, and sharing in, his family’s joint resources.
To compare flows of disposable income at different points in time, in different countries, or even in different locations within a country, the measured values of such incomes must be adjusted to allow for variations in the cost of living. Even after such adjustments have been made, disposable income should not be confused with standard of living or with economic welfare, the actual standard of consumption that a person has achieved.
FindLaw
The income remaining to an individual after deduction of taxes.
The income of a debtor in bankruptcy that is not necessary to support the debtor or the debtor's dependents.
Wikipedia
Disposable income is gross income minus income tax on that income. In national accounts definitions, personal income, minus personal current taxes equals disposable personal income. Subtracting personal outlays (which includes the major category of personal (or, private) consumption expenditure) yields personal (or, private) savings.



