VOYAKILOID, meaning "Grouching Vocaloid," pertains to Fanmade Vocaloids representing failure of purpose and failure of proper singing.
This name was from "boyaku" (γΌγγ; to grouch) and "loid," and the trend started when Caffein illustrated and drew inspiration from 2ch for the first character of this class of Vocaloids: Haku Yowane. Since then, other fans added to the family of Voyakiloids, deriving their personalities from none other than Haku herself, although this can vary greatly. Many official Vocaloids have a Voyakiloid equivalent.
Voyakiloid are commonly depicted in a theme color of gray and purple, with white hair and red eyes. They are notably pale skinned and have under-eye circles, usually because of stress. They are portrayed as being depressed or grouchy, and addicted to something such as alcohol, coffee, or cigarettes--though this varies depending on the character.
Their state of depression is the result of failure to complete a task, which is usually singing.