Vaisesika Sūtra 3.1.11

विरोध्यभूतं भूतस्य ॥११॥

virodhyabhūtaṁ bhūtasya ॥11॥

[विरोधि-अभूतम् (virodhi-abhūtam) - that which has become opposed; भूतस्य (bhūtasya) - of the existing (thing).]

That which has become opposed to what was.