|1.||added or appearing accidentally or unexpectedly|
|2.||(of a plant or animal part) developing in an abnormal position, as a root that grows from a stem|
|[C17: from Latin adventīcius coming from outside, from adventus a coming]|
adventitious ad·ven·ti·tious (ād'věn-tĭsh'əs, -vən-)
Arising from an external source or occurring in an unusual place or manner; extrinsic.
Occurring accidentally or spontaneously, not caused by heredity.