Five faults

The five faults (Tib. ཉེས་པ་ལྔ་, nyepa nga; Wyl. nyes pa lnga) are defects to be overcome by means of the eight antidotes when practising shamatha meditation. They are mentioned in Maitreya’s Distinguishing the Middle from Extremes (Skt. Madhyantavibhanga).

Laziness (Tib. ལེ་ལོ་, Wyl. le lo) – there are three kinds: (i) lethargy, (ii) attachment to negative behaviour, and (iii) despondency
Forgetting the instructions (Tib. བརྗེད་པ་, Wyl. brjed pa). These two are obstacles in the beginning.
Dullness and Agitation (Tib. བྱིང་རྒོད་, Wyl. bying rgod) – there are subtle and gross forms to both dullness (Tib. བྱིང་པ་, Wyl. bying pa) and agitation (Tib. རྒོད་པ་, Wyl. rgod pa). These are obstacles during the actual practice of meditation.^[1]
Under-application (Tib. འདུ་མི་བྱེད་པ་, Wyl. ‘du mi byed pa) – this occurs when one recognizes the presence of dullness or agitation but fails to apply the antidote
Over-application (Tib. ཧ་ཅང་འདུ་བྱེད་པ་, Wyl. ha cang ‘du byed pa) – this occurs when one recognizes the presence of dullness or agitation, applies the antidote, and then continues to apply it even when dullness or agitation are no longer present. These are obstacles to the further development of one’s meditation.

Notes

↑ Kamalashila in his Stages of Meditation (and Vimalamitra in his text of the same name) list dullness and agitation separately, making a total of six faults.