In the eCommerce edition of the CM Tooltip Glossary plugin it is possible to select and enable a Wikipedia API and add it to the term page and to the tooltip content.
The content taken from Wikipedia is generated automatically and can also include images, tables and all other content that was originally included in the Wikipedia term definition.
If you want to write your own definition for just some of your terms, and have others displaying wikipedia content, you can override the plugin settings by checking the metaboxes on the term page editor, as shown in the image bellow: