Happening or carried on according to chance rather than design or inherent nature. The adventitious meeting with an old friend led to an unexpected business opportunity.
Not native; coming from outside; not inherent or innate. The adventitious roots of the plant helped it to stabilize in the loose soil.
Formed accidently or appearing in an abnormal or unusual position, especially in botany and zoology. Adventitious buds developed on the stem after it was damaged.