This paper presents a novel approach for resolving ambiguities in concepts that already reside in semantic databases such as Freebase and DBpedia. Different from standard dictionaries and lexical databases, semantic databases provide a rich hierarchy of semantic relations in ontological structures. Our disambiguation approach decides on the implied sense by computing concept similarity measures as a function of semantic relations defined in ontological graph representation of concepts. Our similarity measures also utilize Wikipedia descriptions of concepts. We performed a preliminary experimental evaluation, measuring disambiguation success rate and its correlation with input text content. The results show that our method outperforms well-known disambiguation methods.