नमस्ते अस्तु भगवन् विश्वेश्वराय महादेवाय् त्र्यम्बकाय त्रिपुरान्तकाय त्रिगाग्निकालाय कालाग्निरुद्राय नीलकण्ठाय मृत्युञ्जयाय सर्वेश्वराय सदाशिवाय श्रीमन्महादेवाय नमः।

namaste astu bhagavan viśveśvarāya mahādevāya trymbakāya tripurāntakāya trigāgnikālāya kālāgnirudrāya nīlakaṇṭhāya mṛtyuñjayāya sarveśvarāya sadāśivāya śrīmanmahādevāya namaḥ |

This mantra is not in Veda and is a subsequent addition. But this mantra is invariably chanted as part of Śrī Rudram.

This mantra begins by paying salutations to Rudra as Bhagavān. He is addressed with eleven attributes.

viśveśvarāya – Lord of the universe;

mahādevāya – supreme among gods;

trymbakāya – the one who has three eyes (sun, moon and fire);

tripurāntakāya – the one who has burnt three forts (subtly conveying three states of normal consciousness –active, dream and deep sleep states);

trigāgnikālāya – There are three types of sacrificial fire gārhapatya, āhavanīya, and dakṣiṇa agni-s. Rudra holds all the three types of sacrificial fires within;

kālāgni-rudrāya - at the time of annihilation, signalling the end of a cosmic cycle, Kālāgni Rudra embraces the universe, dance of death and destruction. This is called tāṇḍava. Rudra dances to the drum beats causing every single object in all the universes merge into a divine unity.  The fire that burns the universes dissolves into water, water into wind, wind into ākāśa, ākāśa into multitude of deva-s and deva-s into the Brahman.  At this stage puruṣa and prakṛti are separated and merge into Rudra.  Rudra alone exists witnessed by Śaktī. This dance of Śiva is called pulsating process of creation and annihilation;

nīlakaṇṭhāya – Rudra is worshiped in 25 forms as per āgama śāstra and nīlakaṇṭha is one among them. Purānic Shiva has a blue throat due to swallowing of deadly poison while churning the ocean of milk;

mṛtyuñjayāya – the one who has conquered death. He has conquered god of death Yama and hence this name. Subtly this conveys that He is beyond any time limit, as birth and death are controlled y time;

sarveśvarāya – He is the Lord of the entire universe; He is Brahman, beyond whom, nobody is there. He is Ultimate and Absolute;

sadāśivāya – literally it means always kind, happy and prosperous. This is one of the manifestations of Shiva. Sadā means ever and Śiva means auspicious.  The Sadāśivā form of the Brahman is the most auspicious form.  In the stage of Sadāśivā tattva, icca śakti or the will to create is predominant.  The concept of “I am this” begins to dawn (this stage is not “I am That”), where perfect purity is not yet attained. In this stage universal consciousness is discovered.

Śrīman-mahādevāya – Śrī indicates His auspiciousness and śrīman is a word that conveys highest respect. Mahādeva, the Supreme God.

namaḥ - we offer our salutations to you Rudra, again.

In the next seven anuvāka-s, every mantra ends with नमः namaḥ (approximately 100 mantras). Every aspect of Rurdra is being worshiped in the next seven anuvāka-s.

नमो हिरण्यबाहवे सेनान्ये दिशां च पतये नमः॥

namo hiraṇyabāhave senānye diśāṁ ca pataye namaḥ || (2:1)

Meaning:

His hands are like gold or He is wearing gold ornaments, symbolizing His auspiciousness. He is the chief of His army, present in all the (ten) cardinals. Salutation to you Rudra.

Notes:

Hiraṇya means gold. There are several references to hiraṇya. His body is shining as Shiva is always described as Prakāśa or Self-effulgent. Secondly, hiraṇya always refers to imperishable matter, which subtle conveys that is He is beyond time (kāla). Attributes of Rudra are being worshiped now.

(Further reading: The souls originated from the hiraṇyagarbha or the golden egg. This is so called, as it is born from a golden egg, formed out of the seed deposited in the waters when they were produced as the first creation of the Self-existent This seed became a golden egg, resplendent as the sun, in which the Self-existent Brahma was born as Brahmā the Creator, who is therefore regarded as a manifestation of the Self-existent. This is held as the fourth act of the Brahman, tirodhāna, or the great dissolution or the act of concealment.  The difference between destruction and annihilation is significant.  Destruction is the death of a single organism and dissolution is the Supreme process of the Brahman, wherein He makes the entire universe to dissolve and merge unto Himself.  At this stage the universe becomes non-existent.  There will be no continents, no mountains, no oceans, none of the basic elements (Pañca bhūta-s) exist.  Such an act of the Brahman is called mahā-pralayā.  This happens when Śiva begins His mahā-pralaya tāṇḍava or the cosmic dance.  When Śiva performs this dance of annihilation, universe gradually gets dissolved unto Him.  The reverse modifications take place and penultimately there exists only the five basic elements.  Finally these five elements too, dissolve into Śiva.)

नमो वृक्षेभ्यो हरिकेशेभ्यः पशूनां पतये नमः॥

namo vṛkṣebhyo harikeśebhyaḥ paśūnāṁ pataye namaḥ || (2:2)

Meaning:

Salutations to Rudra, who is in the form of trees with green foliage and the Lord of all beings (paśu - individual souls as distinct from the divine Soul, which includes all the being in the universe). Paśu also refers to those who are bound by karma.

Notes:

Trees here mean births and deaths. Taittirīya Upaniṣad (I.10) says. “I am the inspirer of this tree, called world”. The trees mentioned represent different worlds (together called universe) and all these worlds are rooted to Rudra. Foliage represent paśu-s. Paśūnāṁ pataye says that Rudra is the protector of all the paśu-s.

{Further reading 1: There are said to be five types of sacred trees and kadamba tree is one among them. These five sacred trees said to represent the four components of antaḥkaraṇa viz. mind, intellect, consciousness and ego and the fifth being the heart where the soul is said to reside (Some modern interpretations point out that the soul resides within the pineal gland, the gland of divinity).  The smell of these flowers is compared to the modifications of the mind.

Further reading 2: Sanaka, Sana, Sanatkumāra, and Sanāndana are the four great sages who were initiated by Dakṣiṇāmūrti. There was a huge banyan tree under which was seated young Dakṣiṇāmūrti with his aged disciples mentioned above.  The banyan tree is the symbolic manifestation of macrocosm from microcosm.  From a tiny seed of banyan, a huge tree of banyan grows. This is compared to the formation of gross from subtle. Initiation takes place without any words being exchanged.}