parihāna-dhamma: 'liable to decline'. "Now, someone reaches the attainments (absorptions: jhāna, q.v.) of the fine-material or immaterial sphere (s. avacara). But he does not reach them according to his wish, and not without trouble and exertion; and not according to his wish with regard to place, object and duration, does he enter them, or rise therefrom. Therefore it is well possible that such a monk, through negligence, may lose these attainments. Such a person is said to be liable to decline" (Pug. 5).

Buddhist Dictionary, Manual of Buddhist Terms and Doctrines, by NYANATILOKA MAHATHERA