With the continual increase of the volume of available information on the web, information access and knowledge management become challenging. Thus, adding a semantic dimension to the Web, by the deployment of ontologies, contributes to solve many problems. In the context of the semantic Web, ontologies improve the exploitation of Web resources by adding a consensual field of knowledge. The need for using domain ontology for information retrieval (IR) has been explored by some approaches to better answer users' queries. However, ontology in IR system requires a regular updating, especially the addition of new concepts and relationships. In fact, IR systems are generally based on few number of domain ontology that cannot be extended. This paper proposes an incremental approach for domain ontology learning. This approach is designed to be integrated into IR system based on ontology. It is based on an ontological representation called "Metaontology." The approach presented was tested and evaluated on a tourism ontology built from results of an online IR system based on ontology.