Śrī Rūpa Goswami defines rāgānugā bhakti as follows.

virājantīm abhivyaktāṁ vraja-vāsī janādiṣu |rāgātmikām anusṛtā yā sā rāgānugocyate ||rāgānugā-vivekārtham ādau rāgātmikocyate ||iṣṭe svārasikī rāgaḥ paramāviṣṭatā bhavet | tan-mayī yā bhaved bhaktiḥ sātra rāgātmikoditā ||sā kāmarūpā sambandha-rūpā ceti bhaved dvidhā ||

This is a nested definition. Śrī Rūpa defines rāgānugā in terms of another term- rāgātmikā bhakti. He further defines the term ‘rāga’. We will examine the definitions in reverse order, starting with the term rāga.

rāga = iṣṭe svārasikī paramāviṣṭatā.

Śrī Jīva Goswami explains the meaning of these individual terms.

iṣṭe = svānukūlya-viṣaye, in the object of one’s favorable service. svārasikī = svābhāvikī, by it’s very nature. paramāviṣṭatā = complete absorption, whose cause (tasyā hetuḥ) is desire (tṛṣṇā) made of prema (prema-maya). Putting all this together, we get

rāga is complete and natural absorption in the object of one’s favorable service.

The interesting thing here is that rāga itself is called absorption, although rāga is that which gives or brings absorption. Śrī Jīva notes that such a definition is acceptable with the example of ‘ghee is life’. Ghee is not actually life, but because it increases life, its called life. In the same way, rāga is called absorption because it brings complete absorption.

rāgātmikā bhakti = tan-mayī yā bhaved bhaktiḥ

that bhakti which is made of rāga or impelled exclusively (tad-eka-preritā) by rāga, is called rāgātmikā bhakti

This rāgātmikā bhakti *cannot* be performed by sādhakas. It is present in the eternal devotees of Vraja. To make this point clear, Śrī Rūpa Goswami qualifies it further:

That bhakti is called rāgātmikā which exists (virājantīm) in its manifest form (abhivyaktāṁ) in the residents of Vraja (vraja-vāsī janādiṣu).

Here then is the definition of rāgānugā bhakti:

rāgātmikām anusṛtā yā sā rāgānugocyate: That is rāgānugā bhakti which follows rāgātmikā bhakti.

A few things to note:

1. rāgātmikā bhakti is performed by siddhas i.e. devotees in the spiritual world. By definition, rāga arises from prema, which is not to be found in the material world.
2. The word ‘anuga’ means ‘following’. rāgānugā bhakti is not the same as rāgātmikā bhakti, but it follows rāgātmikā bhakti. A sādhaka performs rāgānugā bhakti.
3. rāgānugā bhakti is a sādhanā, just like vaidhī bhakti. These are two different types of sādhanās, which bring two different types of results. vaidhī bhakti does not and cannot turn into rāgānugā bhakti.