Found on Urban Dictionary, subsequently removed for reasons unknown:
Someone who acts against the interests of the organization he’s with, often in favor of some other organization he may be secretly working for instead — a mole.
Named after former SGI CEO Richard Belluzzo, who killed IRIX and MIPS at SGI in favor of NT on Itanium. Right before that, he was Executive VP at HP, where his main accomplishment was killing HPUX on PA-RISC in favor of NT on Itanium. Impressively, this guy single-handedly killed two of the leading 64-bit computing platforms in favor of Itanium-on-NT before Itanium even launched.
Despite those being disastrous decisions for the companies he was supposedly “working” “for”, Belluzzo did well for himself, being given a President and COO job at Microsoft after killing SGI and HP’s 64-bit-computing strategies.
Those acts — along with the reward from Microsoft — got him the nickname “The Microsoft Mole” (Google “Microsoft mole Belluzzo”) in those companies, and occasionally the term “a belluzzo” is used to describe someone who seems to be acting in the interest of a different company than the one he works for.
“Our new CFO’s such a belluzzo — approving enormous expenses paid to his wife’s company, while rejecting the expenses we need to do our work.”
See also: elop, itanic.