This study describes the methodology used in the development of a WordNet lexicon for the Galician language, and its applications for language processing in the fields of terminology acquisition and ontology learning and management. First, we review the Princeton WordNet lexical model, its multilingual adaptation in the EuroWordNet framework, and its implementation in the Galician WordNet building. Second, we discuss the approach and the resources used in the design of Termonet, a tool for checking and verifying in technical corpora the specialty lexicons embedded in WordNet. This tool performs an identification of the synsets in WordNet belonging to a terminological domain from the semantic relations between the nodes of the lexical network, and validates the terms by means of a semantically disambiguated specialized corpus. Third, we analyze the process of construction of a new semantic categorization of WordNet based on epinonyms and generated automatically by exploring the relations from a terminological perspective. A WordNet epinonym is a noun synset in the semantic network representing the category of the semantic domain to which other synsets will be automatically assigned by algorithms that will evaluate their proximity from a terminological point of view through the cognitive processing of the lexical-semantic relations. Last, we present some applications of the RDF Galician WordNet in the Semantic Web by means of federated queries with lexical and ontological resources available as Linked Open Data (LOD) like DBpedia, BabelNet, Wiktionary and YAGO.