Stands for 'total cost of ownership' - and is a measure of the full cost of ownership of a business asset through its useful life. It includes original cost plus running costs, financial and tax implications. Often used to compare relative costs of lease / rental against ownership. NOT a measure of ROI.
Total Cost Of Ownership - The financial cost in £'s of having an asset involved in a business. It's not an ROI (return on investment) measure because it only refers to cost of utilising an asset rather than the comparison of the costs against the benefits arising from that asset.