From Omics.org

Orfeome or Orfome is the totality of open reading frames(ORF) in biology. ORFs are the most important genetic elements in genomes. They code for proteins. Determining ORFs are done by computer programs such as GenScan. The computer alrorithms are produced by bioinformatists. As ORFs are produced by computer programs, ORFeome(s) are prediction results by definition. Therefore, ORFeome is a bioinformatics concept. This is the case for genomes as genomes are also finalized by computer aligorithms. On the other hand, proteome that includes ORFeome is mostly from experimental data generated by techniques such as mass spectroscopy.
The term ORFeome reflects a new trend in biology that can be succinctly summarized as omics.