In WordPress, you can place one post or article under multiple categories. Similarly, GeoDirectory lets you place one listing under multiple categories. 

Adding Multiple Categories to a Listing

When creating a new listing form, be sure that the Category field is a Multiselect. In such a case, you will be able to place all listings added via that form under multiple categories. 

Alternatively, you can also change that field to Select — in this case, the listings of that particular CPT can be placed under one category only.