What is desultoriness? It is to be a scatter-brain and belongs to the categories of passion-lust, aversion-hatred, and bewilderment-erring. Its function is to obstruct one from becoming free of passion-lust.
It is a mind forced to become distracted from its objective reference through the power of the emotions. The Pandaskadhaprakarana states,

The mind is scattered over the five desirable objects of the sensuous world.

If you think that there is no difference between this and ebullience explained above, you should know that 'ebullience' is a going out towards the pleasurableness of an object one has previously known and therefore belongs to passion-lust. Desultoriness is tied up with all three poisons and is concerned with any object and hence these two states are not similar.

There are six kinds of desultoriness:

1.    Desultoriness qua desultoriness    [ngo bo nyid gyi gYeng ba]
2.    Desultoriness regarding the without    [phyi rol tu gYeng ba]
3.    Desultoriness regarding the within    [nang gyi gYeng ba]
4.    Desultoriness regarding defining characteristics    [mtshan ma'i gYeng ba]
5.    Desultoriness of inappropriate actions    [gnas ngan len gYeng ba]
6.    Desultoriness by rationalization    [yid la byed pa'i gYeng ba]
Desultoriness qua desultoriness refers to the five sensory perceptions. When one is in the state of meditation, one will rise out of it at any moment when any one of the five sensory perceptions takes place; this is to say that the mind is distracted from its state of concentration.

Desultoriness regarding the without  is the going out of the mind towards qualities which do not make one want to stay with them when one has just entered into what is positive through the three activities of listening, thinking, and attending. This is to say that one does not stay with the positive object, but moves towards the opposite.

Desultoriness regarding the within is a craving to relish, a state of elation, depression or indifference in meditation. The reason we speak of internal agitation is that these factorys are the main distractions to concentration.

Desultoriness regarding defining characteristics means to apply oneself to the positive when one thinks that he too should do it because others say, "This is meditation."

Desultoriness of inappropriate action is an inflatedness by the idea of 'I' and 'mine' with reference to the feeling of getting into what is positive while depending on the pitfalls provided by (perverted) views, which take what is perishable as the last word about reality, and by arrogance.

Desultoriness by rationalization  is like giving up the equanimity of the fourth meditation*  for the equanimity of the three lower meditations or to exchange the Mahayana for the Hinayana.

All of these are called distractions in a general way, but this does not mean that they are all proximate emotions. The first one is indeterminate and the last one is positive. The real proximate emotion of desultoriness is the desultoriness regarding the without and the within. An intelligent person should study this distinction carefully.

* The counsel that you must devote yourself to the four levels of meditation means to put into practice intense concentration which will lead you to the excellent state of calm. The first level is threefold in  view of it being a counteragent, a benefit, and a state. Counteragent:Integrated actions which are in accordance with observation and discursiveness removes emotional instabilities such as the desire to torment and the desire to strive after sensuous objects. Benefit: One enjoys the joy and satisfaction which arise from one's solitude. State: the concentrated and integrated state of mind. The second level: The mind having been freed of observation and discursiveness experiences only  joy and satisfaction. The third level: The mind having  been freed of joy  which is an indifference to composite things and introspective understanding experiences only satisfaction. The fourth level: The mind having  been freed of even the satisfaction of purity and equanimity has a feeling tone of equanimity and is integrated concentration. In gaining these four levels of meditation, all frustrations and unhappy states of the mind are overcome.
-Lama Mipham  in his bShes sbring gi mchan 'grel padma dkar po'i phreng ba