That interlopes, or is an interloper.
spec. With negative implication: that undertakes an activity or role, esp. a public office, in the manner of a trade or occupation, e.g. by…
(a) n. the smuggling, distribution, and sale of illegal drugs; (b) adj. involved in the smuggling, distribution, and sale of illegal drugs.
Subcategories:
— in liquor (2)
— sordid or petty trading (3)
— bought or sold by illicit means (1)
— relating to smuggling (5)