Adventitious

a. [ L. adventitius. ] 1. Added extrinsically; not essentially inherent.
Syn. -- accidental; casual; incidental; additional; supervenient; foreign. [ 1913 Webster + PJC ]

To things of great dimensions, if we annex an adventitious idea of terror, they become without comparison greater. Burke. [ 1913 Webster ]

2. (Nat. Hist.) Out of the proper or usual place; as, adventitious buds or roots. [ 1913 Webster ]

3. (Bot.) Accidentally or sparingly spontaneous in a country or district; not fully naturalized; adventive; -- applied to foreign plants. [ 1913 Webster ]

4. (Med.) Acquired, as diseases; not hereditary. AS [ 1913 Webster ]

5. (Med.) Occurring in an unusual place or arising from an external source. Stedman 25 [ PC ]

-- Ad`ven*ti"tious*ly, adv. -- Ad`ven*ti"tious*ness, n. [ 1913 Webster ]