Adventitious

прилагательное [литературно-книжное] 1) случайный; непреднамеренный Синоним(ы): accidental, casual, chance 2) вспомогательный, добавочный, дополнительный

Большой англо-русский словарь

Adventitious

adjective Etymology: Latin adventicius 1. coming from another source and not inherent or innate Example: a Federal house without adventitious later additions 2. arising or occurring sporadically or in other than the usual location Example: adventitious rootsadventitiously adverb

Merriam-Webster's Collegiate Dictionary