Sānanda samādhi , also known as "supreme bliss", is the third level of the four samādhi described in the Yoga Sutras 1:17 by Patanjali. Sānanda: sa- means “with”, ananda means joy, bliss.
Dr. Sarasvati Buhrman
....when people feel blissful sensations during sādhanā, on a gross level the breath is equal in both nostrils, and on the subtle level pranic flow in ida and pingala nadis is balanced. This is called the sushumna breath because the residual prana of the sushuma, the kundalini, flows in sushumna nadi, causing sattva guna to dominate. It creates a feeling of peace. That peace is ananda. In sananda samadhi the experience of that ananda, that sattvic flow, is untainted by any other vrittis, or thoughts, save the awareness of the pleasure of receiving that bliss.
Its equivalent on this site is bliss and peace.