Shorthand for a "very happy engineer". Engineers are often at the bottom of the metaphorical social ladder and thus are typically mean-spirited, neckbearded, lonely individuals. A vheng is one who actually enjoys his lot in life and embraces it in full. They are quite rare, but they are a fascinating group of people. Unfortunately, they are dying out as a result of their inability to talk with women. They have no sexual means of reproduction, but they are currently working on an asexual process involving the right hand and a sock.
Look at Vincent program! You can tell he's a vheng because of how enthusiastically he does his job.
Dude, I asked Vincent if he wanted to go to the beach party, but he said he's studying for chem-e, what a vheng.