From vandal + -ous. Possibly formed by analogy with scandalous.
vandalous (comparative more vandalous, superlative most vandalous)
- vandalistic; resembling vandalism
2001, Iain Borden, Skateboarding, Space and the City: Architecture and the Body[1], →ISBN, page 253:Even usually thoughtful newspapers such as the Washington Post have cited skateboarding as an irresponsible and vandalous activity to be banned from city streets.
- destructive; resembling a vandal
2000, Jefferson S. Chase, Inciting Laughter: The Development of "Jewish Humor" in 19th Century German Culture[2], →ISBN:The word mob [Pöbel] invoked the image of a vandalous rabble and, with it, the specter of the Reign of Terror.