|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
|a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison.|
|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.