The word guru, a noun, means “teacher” in Sanskrit
As a noun the word means the imparter of knowledge (jñāna; Also Persian: Dāna). As an adjective, it means ‘heavy,’ or ‘weighty,’ in the sense of “heavy with knowledge,” heavy with spiritual wisdom,
The word has its roots in the Sanskrit gri (to invoke, or to praise), and may have a connection to the word gur, meaning ‘to raise, lift up, or to make an effort’.
A traditional etymology of the term “guru” is based on the interplay between darkness and light. The guru is seen as the one who “dispels the darkness of ignorance.” In some texts it is described that the syllables gu (गु) and ru (रु) stand for darkness and light, respectively.
Another etymology of the word “guru” found in the Guru Gita, includes gu as “beyond the qualities” and ru as “devoid of form”, stating that “He who bestows that nature which transcend the qualities is said to be guru”. The meanings of “gu” and “ru” can also be traced to the Sutras indicating concealment and its annulment.
WHO IS A GURU?
Guru is one who has full Self-illumination and who removes the veil of ignorance in deluded Jivas. Guru, Truth, Brahman, Ishvara, Atman, God,Omare all one. The number of realized souls may be less in this Kali Yuga when compared with the Satya Yuga, but they are always present to help the aspirants. They are always searching for the proper Adhikarins.
Guru is Brahman Himself. Guru is Ishvara Himself. Guru is God. A word from him is a word from God. He need not teach any. Even his mere presence or company is elevating, inspiring and soul-stirring. The very company itself is self-illumination. Living in his company is spiritual education. That which comes out of his lips is all Vedas or gospel-truth. His very life is an embodiment of Vedas. Guru is your guide or spiritual preceptor, real father, mother, brother, relative and intimate friend. He is an embodiment of mercy and love. His tender smile radiates light, bliss, joy, knowledge and peace. He is a blessing to the suffering humanity. Whatever he talks is Upanishadic teaching. He knows the spiritual path. He knows the pitfalls and snares on the way. He gives warning to the aspirants. He removes obstacles on the path. He imparts spiritual strength to the students. He showers his grace on their heads. He takes their Prarabdha even on his head. He is the ocean of mercy. All agonies, miseries, tribulations, taints of worldliness, etc., vanish in his presence.
It is he who transmutes the little Jivahood into great Brahmanhood. It is he who overhauls the old, wrong, vicious Samskaras of the aspirants and awakens them to the attainment of the knowledge of Self. It is he who uplifts the Jivas from the quagmire of body and Samsara, removes the veil of Avidya, all doubts, Moha and fear, awakens Kundalini and opens the inner eye of intuition.
The Guru must not only be a Srotriya but a Brahma-Nishtha also. Mere study of books cannot make one a Guru. One who has studied Vedas and who has direct knowledge of Atman through Anubhava can only be considered a Guru. If you can find peace in the presence of a Mahatma, and if your doubts are removed by his very presence you can take him as your Guru.
A Guru can awaken the Kundalini of an aspirant through sight, touch, speech or mere Sankalpa (thought). He can transmit spirituality to the student just as one gives an orange-fruit to another. When the Guru gives Mantra to his disciples, he gives it with his own power and Sattvic Bhava.
The Guru tests the students in various ways. Some students misunderstand him and lose their faith in him. Hence, they are not benefited. Those who stand the tests boldly come out successful in the end. The periodical examinations in the Adhyatmic University of Sages are very stiff indeed. In days of yore the tests were very severe. Once Gorakhnath asked some of his students to climb up a tall tree and throw themselves head downwards on a very sharp Trident (Trishul). Many faithless students kept quiet. But one faithful student at once climbed up the tree with lightning speed and threw himself down. He was protected by the invisible hand of Gorakhnath.
Spiritual knowledge is a matter of Guruparampara. It is handed down from a Guru to his disciple.