The term “abhidharma” has been used at least in two meanings: (a) [Discourse] about dharma (truth) and (b) Dharma (truth or teaching) about [nirvana, etc.]. The original meaning of the term seems to have been the former (a), and one may say that the second meaning (b) was added later in the history of Abhidharma Buddhism. Vasubandhu in his Abhidharmakosabhasya states that abhidharma is of two kinds: the ultimate and the conventional. The author of the work defines the ultimate abhidharma in terms of the second meaning (b) of abhidharma.
Commenting on the definition of the ultimate abhidharma given in the Abhidharmakosasastra (1, 2a) Vasubandhu states: anasravah pañcaskandhako 'bhidharma ity (Abhidharma is free from asrava (mental defilements) and is accompanied by five skandhas (constituent elements)). Xuanzang has translated the passage in the following sense: The five skandhas that are free from asravas are called abhidharma. The Peking edition of the Tibetan translation of the passage (Tibetan Tripitaka, Suzuki Foundation, Vol. 115, p. 127, f. 4, 11. 3-4) has the same meaning as Xuanzang's translation. The expression “pañcaskandhaka,” however, does not mean five skandhas, but rather that which is accompanied by five skandhas.