("nectar of the feet") Literally, the water (or other liquid) in which one's guru's feet or god representations are washed.
It is consumed by the student or devotee (bhakta) as a symbol of subordination and as a means of receiving grace and benefits.
By extension, the term may apply to any liquid consumed by devotees as a sign of the deity's favor, regardless of whether it has been used for washing (snana).
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