'impurities', corruptions, imperfections (a frequent rendering by 'defilements' is better reserved for kilesa).

A list of 16 moral 'impurities of the mind' (cittassa upakkilesa) is mentioned and explained in M.7 & 8 (WHEEL 61/62):

• 1. covetousness and unrighteous greed (abhijjhā-visamalobha),
• 2. ill will (vyāpāda),
• 3. anger (kodha),
• 4. hostility (upanāha),
• 5. denigration (makkha),
• 6. domineering (palāsa),
• 7. envy (issā),
• 8. stinginess (macchariya),
• 9. hypocrisy (māyā),
• 10. fraud (sātheyya),
• 11. obstinacy (thambha),
• 12. presumption (sārambha),
• 13. conceit (māna),
• 14. arrogance (atimāna),
• 15. vanity (mada),
• 16. negligence (pamāda).

There are 3 groups of upakkilesa pertaining to meditation:

(a) 9 mental imperfections occurring in 'one devoted to higher mental training' (adhicitta); 3 coarse ones - evil conduct in deeds, words and thoughts; 3 medium - thoughts of sensual desire, ill will and cruelty; 3 subtle - thoughts about one's relatives, one's country and one's reputation (A.III.100).

(b) 18 imperfections in the practice of mindfulness of breathing (Ānāpāna-sati), mentioned in Pts.M., Ānāpāna-kathā (tr. in Mindfulness of Breathing, by Ñānamoli Thera (p. 60; BPS).

(c) 10 'imperfections of insight' (-meditation, vipassanūpakkilesa); s. visuddhi V.