interloper

One that interferes with the affairs of others, often for selfish reasons; a meddler.

One that intrudes in a place, situation, or activity.

One that trespasses on a trade monopoly, as by conducting unauthorized trade in an area designated to a chartered company.

A ship or other vessel used in such trade.

One who trades without license.

One who interferes obtrusively or officiously; one who thrusts himself into a station to which he has no claim, or into affairs in which he has no interest.

One who interlopes; one who unlawfully intrudes upon a property, a station, or an office; one who interferes wrongfully or officiously.

An unlicensed or illegitimate trader.

One who interferes, intrudes or gets involved where not welcome, particularly a self-interested intruder.