This strong definition most often appeals to professionals and people whose jobs require years of training and study, such as doctors, lawyers and accountants. Under this definition, you are considered disabled if you cannot perform the duties of your regular occupation and are not gainfully employed.
This is the strongest definition and most likely to be offered only to high-end professional jobs. Under the own occupation definition, you are deemed disabled if you cannot perform the main duties of your own occupation, regardless of whether or not you are gainfully employed. For example, a surgeon could lose his hands and be deemed disabled, even though he might find a job teaching or consulting.
The most common definition used for blue-collar workers, you are deemed disabled if you cannot perform the duties of any occupation for which you are reasonably suited. It is a much stricter definition to meet due to the fact that as long as you can work in a different job, you are not considered disabled.