| Abbreviation | Definition |
|---|---|
| MCB | McCoy Corporation |
| MDA | MacDonald, Dettwiler and Associates Ltd. |
| MDA | MacDonald, Dettwiler, and Associates LTD. |
| MDF | Mediagrif Interactive Technologies Inc. |
| MDF | Mediagrif Interactive Technologies Incorporated |
| MDG | Medicago, Inc. |
| MDI | Major Drilling Group International Inc. |
| MDI | Major Drilling Group International Incorporated |
| MDM | Mineral Deposits Limited |
| MDN | MDN Inc. |
| MDN | MDN Incorporated (de-listed) |
| MDN | MDN Incorporated (de-listed) |
| MDZ | MDC Partners Inc. |
| MDZ | MDC Partners Incorporated (de-listed) |
| MDZ | MDC Partners Incorporated (de-listed) |
| ME | Moneta Porcupine Mines, Inc. |
| MEG | MEG Energy Corp. |
| MEG | MEG Energy Corporation |
| MEL | Midway Energy, LTD. |
| MEQ | Mainstreet Equity Corporation |