(His Divine Grace A.C. Bhaktivedanta Swami Prabhupada)
"Sometimes the spiritual master is addressed as Prabhupāda. Prabhu means 'the Supreme Personality of Godhead,' and pāda means 'post.' According to Vaiṣṇava philosophy, the spiritual master occupies the post of the Supreme Personality of Godhead, or in other words he is the bona fide representative of the Supreme Lord."
(Śrīmad-Bhāgavatam 4.8.69, Purport)
"The spiritual master is addressed as 'Prabhupāda' because he is a completely self-realized soul. The word pāda means 'position,' and Prabhupāda indicates that he is given the position of prabhu, or the Supreme Personality of Godhead, for he acts on behalf of the Supreme Personality of Godhead. Unless one is a prabhu, or controller of the senses, he cannot act as spiritual master, who is authorized by the supreme prabhu, or Lord Kṛṣṇa. In his verses praising the spiritual master, Śrīla Viśvanātha Cakravartī Ṭhākura writes:
uktas tathā bhāvyata eva sadbhiḥ
'The spiritual master is honored as much as the Supreme Lord because he is the most confidential servitor of the Lord.' "
(Śrīmad-Bhāgavatam 4.23.18, Purport)
"Prabhu means master. And 'Prabhupāda' means many masters who bows down at his lotus feet. That is Prabhupāda."
(Srila Prabhupada Conversation, Seattle, September 24, 1968)
"Prabhu means master. And Prabhupāda means supreme master. That is the meaning."
(Srila Prabhupada Morning Walk, Los Angeles, October 1, 1972)
"We are taught to address others as Prabhu. Prabhu means master; and the leader of the masters is called Prabhupad."
(Srila Prabhupada Letter, May 10, 1970)
"Guru will never say, 'Now I have become God.' No. God does not become. God is always God. So God is God and guru is guru. But, as a matter of etiquette, God is the sevya God, worshipable God, and guru is the worshiper God. Just try to understand. Worshipable God and worshiper God. This is. Sevya bhagavān-sevaka bhagavān. Just like guru is addressed: 'Prabhupāda.' Prabhu means 'the Lord' and pāda means 'the position.' 'One who has taken the position of the Lord.' The same thing: sākṣād-dharitvena, prabhupāda. These are the terms, one who is serious to study this science of God, they'll learn all these things. So one who is very serious to understand the science of God, for him a guru is required."
(Srila Prabhupada Lecture, London, August 22, 1973)
"Prabhupāda means the title, or the respect, which is given to the Supreme Personality of Godhead. That is called... Prabhu means master, and pāda means maryādā, or the respect, or the distinction.
So bhagavad-dūta, those who are strictly following the dictation of Kṛṣṇa under strict disciplinary chain of disciplic succession, he is Kṛṣṇa's representative, and he should be given all the respect. Sākṣād-dharitvena samasta-śāstraiḥ (Śrī Śrī Gurv-aṣṭaka 7). That is the verdict of all śāstras. And those who are actually Vaiṣṇava, they follow this instruction."
(Srila Prabhupada Lecture, Calcutta, January 6, 1971)
Guest: Prabhupāda, what is the meaning of the word "Śrīla"?
Prabhupāda: Śrīla is... Just like we say "Śrī" to the ordinary person. And Śrīla to very respectable person.
Prabhupāda: La, yes. Śrī means beauty, and la means līlā. So "one who is invested with both beauty and the power to understand the līlā of Kṛṣṇa."
(Srila Prabhupada Morning Walk, Los Angeles, December 21, 1973)
"The pure Vaiṣṇava is addressed as prabhu, and this address is an etiquette observed between Vaiṣṇavas. When many prabhus remain under the shelter of the lotus feet of another prabhu, the address Prabhupāda is given. Śrī Nityānanda Prabhu and Śrī Advaita Prabhu are also addressed as Prabhupāda. Śrī Caitanya Mahāprabhu, Śrī Advaita Prabhu and Śrī Nityānanda Prabhu are all viṣṇu-tattva, the Supreme Personality of Godhead, Lord Viṣṇu. Therefore all living entities are under Their lotus feet. Lord Viṣṇu is the eternal Lord of everyone, and the representative of Lord Viṣṇu is the Lord's confidential servant. Such a person acts as the spiritual master for neophyte Vaiṣṇavas; therefore the spiritual master is as respectable as Śrī Kṛṣṇa Caitanya or Lord Viṣṇu Himself. For this reason the spiritual master is addressed as Oṁ Viṣṇupāda or Prabhupāda. The ācārya, the spiritual master, is generally respected by others as Śrīpāda, and the initiated Vaiṣṇavas are addressed as Prabhu. Prabhu, Prabhupāda and Viṣṇupāda are described in revealed scriptures like Śrīmad-Bhāgavatam, Caitanya-caritāmṛta and Caitanya-bhāgavata. In this regard, these scriptures present evidence accepted by unalloyed devotees.
The prākṛta-sahajiyās are not even worthy of being called Vaiṣṇavas. They think that only caste gosvāmīs should be called Prabhupāda. Such ignorant sahajiyās call themselves vaiṣṇava-dāsa-anudāsa, which means the servant of the servant of the Vaiṣṇavas. However, they are opposed to addressing a pure Vaiṣṇava as Prabhupāda. In other words, they are envious of a bona fide spiritual master who is addressed as Prabhupāda, and they commit offenses by considering a bona fide spiritual master an ordinary human being or a member of a certain caste. Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura describes such sahajiyās as most unfortunate. Because of their misconceptions, they fall into a hellish condition."
(Caitanya-caritāmṛta Madhya 10.23, Purport)
"To take shelter of the lotus feet of the Lord means to take shelter of the pure devotees. The pure devotees whose only business is serving are honored by the names Prabhupāda and Viṣṇupāda, which indicate such devotees to be representatives of the lotus feet of the Lord. Anyone, therefore, who takes shelter of the lotus feet of a pure devotee by accepting the pure devotee as his spiritual master can be at once purified. Such devotees of the Lord are honored equally with the Lord because they are engaged in the most confidential service of the Lord, for they deliver out of the material world the fallen souls whom the Lord wants to return home, back to Godhead. Such pure devotees are better known as vicelords according to revealed scriptures. The sincere disciple of the pure devotee considers the spiritual master equal to the Lord, but always considers himself to be a humble servant of the servant of the Lord (CC Madhya 13.80). This is the pure devotional path."
(Śrīmad-Bhāgavatam 1.1.15, Purport)