This is a technical term used in Vedic liturgy to indicate the extracting of the soma juice from the soma stalks, by pressing them. There are two kinds of pressing: kṣullakābhiṣava (the little pressing) and mahābhiṣava (the great pressing). In the kṣullakābhiṣava, the Adhvaryu (one of the principal priests who does most of the ritual acts and recites the mantras from the Yajurveda) places a few soma stalks on one of the lower grinding stones (called upara), pours consecrated water (called nigrābhya) and beats the stalks in three turns consisting respectively of 8, 11 and 12 single beatings. The juice extracted is collected in a cup. In the mahābhiṣava, four priests sitting round the hide that holds the pressing stones (called adhiṣavaṇacarman) beat the stalks in three turns, after sprinkling them with consecrated water, using the crushing stones (called grāvan) for the operation. The whole act is a ceremonial ritual, forming part of Soma sacrifices.
Abhiṣava is also the technical name given to the ceremonial bath taken before religious rites, especially sacrifices.