A creditor whose debt is secured, e.g. by a charge on the property of the debtor; this may take the form of a debenture where a company is concerned. The charge may be a fixed or a floating charge. A fixed charge is one where the actual property is specified; a floating charge is One which attaches to the property of the debtor generally the actual property only becomes known when the debt is payable, when it is said to crystallize.
Reference: The Penguin Business Dictionary, 3rd edt.