adventitious

/ˌæd.vənˈtɪʃ.əs/

Misollar

A rather adventitious source informed me of his past doings.
His arrivals were always adventitious, leaving others little time to prepare.

sifat adjective

From an external source; not innate or inherent, foreign.
Accidental, additional, appearing casually.
Not congenital; acquired.
Developing in an unusual place or from an unusual source.

Manbalar: Wiktionary (Free Dictionary API orqali), Datamuse, Tatoeba (CC BY 2.0 FR), MyMemory.