Vipallāsa: 'perversions' or 'distortions'. - There are 4 perversions which may be either of perception saññā-vipallāsa of consciousness citta v or of views ditthi-v And which are these four? To regard what is impermanent anicca as permanent; what is painful dukkha as pleasant or happiness-yielding; what is without a self anattā as a self; what is impure ugly: asubha as pure or beautiful A. IV, 49. - See Manual of Insight, by Ledi Sayadaw WHEEL 31/32. p.5.
Of the perversions, the following are eliminated by the 1st path-knowledge sotāpatti the perversions of perception, consciousness and views, that the impermanent is permanent and what is not a self is a self; further, the perversion of views that the painful is pleasant, and the impure is pure. By the 3rd path-knowledge anāgāmitā are eliminated: the perversions of perception and consciousness that the impure is pure. By the 4th path-knowledge arahatta are eliminated the perversions of perception and consciousness that the painful is pleasant; Vis.M XXII, 68.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.