adventive

adventive
    adj 1: not native and not fully established; locally or
           temporarily naturalized; "an adventive weed"
    

Adventive \Ad*ven"tive\, a.
   1. Accidental.
      [1913 Webster]

   2. (Bot.) Adventitious. --Gray.
      [1913 Webster]
    

Adventive \Ad*ven"tive\, n.
   A thing or person coming from without; an immigrant. [R.]
   --Bacon.
   [1913 Webster]