Definitions for "Adventive"
Not indigenous, but apparently becoming naturalized.
Introduced to the country. Not endemic
Arrived in the geographical area specified from somewhere else by any means (adjective); not native (non-indigenous) to the area in which it has arrived. Because of its usefulness, this expression deserves far wider use in the literature than it has obtained.
Keywords:  accidental
Keywords:  immigrant, thing, coming, person
A thing or person coming from without; an immigrant.
Keywords:  permanent, plant, particular, area
a plant that has not become permanent in a particular area