Nimitta: mark, sign; image; target, object; cause, condition. These meanings are used in, and adapted to, many contexts of which only the doctrinal ones are mentioned here.
1. 'Mental reflex-image', obtained in meditation. In full clarity, it will appear in the mind by successful practice of certain concentration-exercises and will then appear as vividly as if seen by the eye. The object perceived at the very beginning of concentration is called the preparatory image parikamma-nimitta The still unsteady and unclear image, which arises when the mind has reached a weak degree of concentration, is called the acquired image uggaha-nimitta An entirely clear and immovable image arising at a higher degree of concentration is the counter-image patibhāga-nimitta As soon as this image arises, the stage of neighbourhood or access concentration upacāra-samādhi is reached. For further details, see: kasina, samādhi.
2. 'Sign of previous kamma' kamma-nimitta and 'sign of the future destiny' gati-nimitta these arise as mental objects of the last kammic consciousness before death maranāsanna-kamma see: kamma, III,
3. 'Outward appearance': of one who has sense-control it is said that he does not seize upon the general appearance' of an object na nimittaggāhī M. 38, D. 2; expl. Vis I, 54f; see sīla.
4. 'Object': the six objects, i.e. visual, etc. rūpa-nimitta S. XXII, 3. Also, when in explanation of animitta-ceto-vimutti signless deliverance of mind see: ceto-vimutti vimokkha it is said, sabba-nimittānam amanasikārā it refers to the 6 sense-objects Com. to M. 43, and has therefore to be rendered;by paying no attention to any object or object-ideas.; - A pleasant or beautiful object subha-nimitta is a condition to the arising of the hindrance of sense-desire; a 'repellent object' patigha-nimitta for the hindrance of ill-will; contemplation on the impurity of an object asubha-nimitta see: asubha is an antidote to sense-desire.
5. In Pts.M. II, in a repetitive series of terms, nimitta appears together with uppādo origin of existence, pavattam continuity of existence, and may then be rendered by 'condition of existence.'
Maha Thera Nyanatiloka. Manual of Buddhist Terms and Doctrines, Buddhist Publication Society, first edition 1952.