Jhāna meditation defination

I am so sorry for the long answer. It's required all of this knowledge to understand the meditation's idea.

What is jhāna?

Jhāna (concentration meditation) is the meditation method to cease the desire (chanda-rāga) of the world (loka) by changing mind's attention to the opposite object of the world.

What is the world?

Living being (satta) is the world (loka), 5 clinging-aggregates (upādāna-khandha[1][2]).

Loka means breakable thing. And what we can notice 3 characteristics must be break, breakable. What is unstable (anicca), stressful (dukkha), and non-self (anattā) is what we can notice it's instability-characteristic (anicca-lakkhaṇa), e.g. it's arising and vanishing, stress-characteristic, e.g. it's stressing to arise and to vanish in every millisecond, and uncontrollable characteristic, e.g. it's variant variables.

Each aggregate has 3 characteristics, so every aggregate (pañca-khandha) is breakable, and it is called Loka. There are 2 kinds of breakable aggregates, lokiya (with clinging) and lokuttara (no clinging). However the practitioner should comprehend only clinging aggregates (upādāna-khandha) to meditate insight meditation, Buddha called clinging aggregates (upādāna-khandha), in first noble truth, not only aggregates (khandha).

The genius people can notice 3 characteristics of every living being, so they try to cease all possible cases of living beings' rebirth by the meditation.

There are many method of the meditation of those genius people which doing the difference methods and each method causes the difference results, some is not able to pause any world, some can pause 5 string world (kāma loka), some can pause form concept world (rūpa loka), some can cease all worlds (kāma loka/rūpa loka/arūpa loka).

How many kinds of jhāna?

There are 3 kinds of jhāna:

1. Form jhāna (rūpa jhāna) - meditation of changing mind's attention form five strings world (kāma-loka) to form's concept world (rūpa-paññatti-loka) to disable 5 sense attachments arising (kāmachandarāga). This meditation's step, 1st-4th jhāna, pause attachment of five strings and mental factors which can drop the quality of concentration down to five strings world. The attained people are going to reborn in the world without five string attachment, but it still has forms, such as eyes to watch the form to meditate rūpa-jhāna.
2. Formless jhāna (arūpa jhāna) - meditation of changing mind's attention form form's concept world to formless world (arūpa-loka) to disable all form arising, which make rūpa jhāna&world still nearby five strings attachment. This meditation change the object to detach from mind and mental factors (arūpa-loka) as much as they can. However, it's useless, the number of mental factors still be the same, 30 factors, from the 1st formless jhāna to the 4th formless jhāna. The attained people are going to reborn in the world without form, but it still have mind and mental factors (nāma-khandha).
3. Three characteristic jhāna (lakkhaṇa-jhāna) - vipassanā; insight meditation. Meditation of changing mind's attention form all worlds to nibbāna (cessation of world). The attained magga people do not reborn any more in maximum 7 rebirths.

Jhāna bases vipassanā, especially for the practitioner who attach five strings strongly (taṇhā-carita).

How to disable 5 sense attachment?

Keeping the sixth sense mind on concept object (paññatti;paṭibhāga-nimitta) by practice to change the the sixth sense memory of the five strings (kāmaguṇa) to concept object (paññatti;paṭibhāga-nimitta) then meditate that practice to go on for a long period, a hour or a day.

How to disable all form arising?

Keeping the sixth sense mind on the object which has no any relation with form (arūpa) by practice to change the the sixth sense memory of form concept (rūpa-paññatti;paṭibhāga-nimitta) to formless object (arūpa) then meditate that practice to go on for a long period, a hour or a day.

What is the problem?

The jhāna practitioner still keep the self attachment of their meditation mind&mind factors as "it's mine. It's me, not the other. It's myself, so I can control it". This is the reason why we need Buddha.

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See Ma.Mu. Cūḷasīhanādasutta, Mahādukkhakkhandhasutta, the path of purification in pathavīkasiṇa chapter and aruppā chapter, and this article.