| Adventitious 1. (a.) Added extrinsically; not essentially inherent; accidental or causal; additional; supervenient; foreign. 2. (a.) Out of the proper or usual place; as, adventitious buds or roots. 3. (a.) Accidentally or sparingly spontaneous in a country or district; not fully naturalized; adventive; -- applied to foreign plants. 4. (a.) Acquired, as diseases; accidental. Thesaurus Entries accessory, accidental, additional, adscititious, aleatory, appurtenant, ascititious, auxiliary, casual, causeless, chance, chancy, circumstantial, collateral, conditional, contingent, destinal, dicey, extra, fatal, fatidic, fluky, fortuitous, iffy, incidental, indeterminate, inessential, nonessential, occasional, provisional, risky, secondary, subsidiary, superadded, superfluous, supervenient, supplemental, supplementary, uncaused, undetermined, unessential, unexpected, unforeseeable, unforeseen, unlooked-for, unpredictable |