upakkilesa

'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).