A kind of empirical Avagraha (sensation);
inspite of the provision of sense-organ, attention and contact with the object, sometime the sensation of the object together with many of its modes, manifold modes etc. take place and sometime does not take place. (Such conditional or probabilistic sensation is Adhruva Avagrahamati).
satīndriye sati copayoge sati ca viṣayasaṃbaṃdhe kadācit taṃ viṣayaṃ tathā paricchinatti kadācinnetyetadadhruvamavagṛhnātītyupadiśyate.
(TaBhā 1.16 Vṛ)