आचार (ācāra)्य (ācārya) a m. ‘knowing or teaching the आचार (ācāra) or rules’, a spiritual guide or teacher (especially one who invests the student with the sacrificial thread, and instructs him in the Vedas, in the law of sacrifice and religious mysteries [Manu-smṛti (Title) ii, 140 ; 171 ]), Atharva-veda (Title) ; Śatapatha-brāhmaṇa (Title) &c. [ID=22935]
— Monier-Williams Sanskrit-English Dictionary (1899)