Theme Organic Group Entity Reference on user profile
You need to create an entity reference view and use it for your og_groups_ref field. In Views where you click Add, you will see entity reference view next to block, page etc.

Create the view to show the groups and the add fields for title and description. Place description above title and exclude it from display. 

Rewrite the title in field settings to something like [title] -[description]. The replacement patterns are in the view field settings.

Go back to your groups audience field settings (main settings, not widget) and choose entity reference view instead of organic groups or simple. Use the view you created.