Added extrinsically; perhaps not springing from essence for the subject, but from another origin; international; accidentally or casually acquired: applied to that which doesn't precisely are part of an interest, but which can be superadded or adopted, as in a picture or any other thing of beauty, so it can have additional energy or result.
In botany and zoology, showing up casually, or in an abnormal or uncommon place or destination; occurring as a straggler or away from its natural place or habitation; adventive.
In anatomy, associated with the nature of adventitia: since, the adventitious coat of an artery.
In phytogeography, naturalized from a distant development: opposed to *vicine. A term recommended by Pound and Clements. Compare adventitious, 2.