Kāya: lit: accumulation: 'group', 'body', may either refer to the physical body rūpa-kāya or to the mental body nāma-kāya In the latter case it is either a collective name for the mental groups feeling, perception, mental constructions, consciousness; s. khandha or merely for feeling, perception and a few of the mental constructions see: nāma e.g. in kāya-lahutā etc. cf. Tab. II.. kāya has this same meaning in the standard description of the 3rd absorption jhāna and he feels joy in his mind or his mental constitution kāya and e.g. Pug. 1-8 of the attainment of the 8 deliverances vimokkha, having attained the 8 deliverances in his mind, or his person kāya - kāya is also the 5th sense-organ, the body-organ.
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.