रहस्यम्rahasyamind. in secret, secretly, privately MBh.
indeclinable in secret, secretly, privately MBh.
भक्तोऽसि मे सखा चेति रहस्यं ह्येतदुत्तमम् ॥
कोशःDictionaries
Apte, Monier-Williams and Macdonell at once. Type in any of fifteen scripts and schemes; the word is converted and looked up wherever it is part of a headword.