(1) The mental factor of a strong longing desire either not to be parted from a feeling of happiness, to be parted from a feeling of unhappiness, or for a neutral feeling in deep meditation not to decline. (2) The mental factor of a strong longing desire to experience something in the future that one may or may not be experiencing at present. The Sanskrit term means, literally, "thirst."
Tibetan: སྲེད་པ། sred-pa
J. Hopkins: Attachment