The Texai lexicon is now available in RDF and N3 format. It was created by merging WordNet, OpenCyc mappings, the CMU Pronouncing Dictionary, and an extract from Wiktionary. It features good coverage of English word forms, pronunciations, word senses, glosses, and sample phrases. See the file release section of the SourceForge project:
In particular the file texai-lexicon-1.1.rdf.ZIP contains the compressed file which expands to over 1 GB. The documentation can be found in the file the-texai-lexicon-rdf-file-explained.doc . The RDF file can be easily hosted by a Sesame 2 RDF store available from Aduna at: http://openRDF.org.
See my blog at http://texai.org/blog for my experience installing the Sesame 2 beta release. There are also Java classes defined to operate on the lexicon as persisted in Sesame using the RDF Entity Manager that can be downloaded from the SourceForge project site too.