BVBA is the abbreviation of "Besloten Vennootschap met Beperkte aansprakelijkheid" (private company with limited liability or Ltd.).

In a BVBA the partners are only liable for the company assets.
The capital is tied up in registered and not freely marketable shares. This way it is avoided that shares are transferred to outside parties without approval of the joint partners and that the family character of the company is lost, for example. 
A BVBA is set up by notarial deed and has to comply with a number of accounting and administrative obligations.