Vulky is a slang term used in the 24th century by some Humans as an adjective, a shorthand allusion to the Vulcan species. As such, it suggests a person driven purely by logical concerns, often to a boring, pedantic, or tiresome extent.
The term was used by Jeffrey, The Doctor's holographic son in his family program. (VOY: "Real Life")
It is also used by Kathryn Janeway in the Voyager novel Mosaic. The specific reference is to "vulky Hobbes Johnson."