The Mahamrityunjaya Mantra , also called the Tryambakam Mantra, is a verse of the Rigveda

Rigveda

The Rigveda is an ancient Indian sacred collection of Vedic Sanskrit hymns...

 (RV 7.59.12).It is addressed to Tryambaka "the three-eyed one", an epithet of Rudra

Rudra

' is a Rigvedic God, associated with wind or storm, and the hunt. The name has been translated as "The Roarer", or "The Howler"....

, later identified with Shiva

Shiva

Shiva is a major Hindu deity, and is the destroyer god or transformer among the Trimurti, the Hindu Trinity of the primary aspects of the divine. God Shiva is a yogi who has notice of everything that happens in the world and is the main aspect of life. Yet one with great power lives a life of a...

. The verse also recurs in the Yajurveda

Yajurveda

The Yajurveda, a tatpurusha compound of "sacrificial formula', + ) is the third of the four canonical texts of Hinduism, the Vedas. By some, it is estimated to have been composed between 1400 and 1000 BC, the Yajurveda 'Samhita', or 'compilation', contains the liturgy needed to perform the...

 (TS 1.8.6.i; VS 3.60)

Along with the Gayatri mantra

Gayatri Mantra

The Gāyatrī Mantra is a highly revered mantra, based on a Vedic Sanskrit verse from a hymn of the Rigveda , attributed to the rishi . The mantra is named for its vedic gāyatrī metre. As the verse can be interpreted to invoke the deva Savitr, it is often called Sāvitrī...

 it is one of the most widely known mantra

Mantra

A mantra is a sound, syllable, word, or group of words that is considered capable of "creating transformation"...

s of contemporary Hinduism

Hinduism

Hinduism is the predominant and indigenous religious tradition of the Indian Subcontinent. Hinduism is known to its followers as , amongst many other expressions...

.

The mantra reads

"ॐ त्र्यम्बकम् यजामहे
सुगन्धिम् पुष्टिवर्धनम् |
ऊर्वारुकमिव बन्धनान्
मृत्योर्मुक्षीय मामृतात् ||"
(IAST

IAST

The International Alphabet of Sanskrit Transliteration is a transliteration scheme that allows a lossless romanization of Indic scripts as employed by the Sanskrit language.-Popularity:...

 transliteration):

This great mantra dedicated to Rudra

Rudra

' is a Rigvedic God, associated with wind or storm, and the hunt. The name has been translated as "The Roarer", or "The Howler"....

 as Mrityunjaya is found in the Rig Veda. It is called the Maha Mrityunjaya mantra, the Great Death-Conquering mantra. It is a mantra that has many names and forms. It is called the Rudra mantra, referring to the furious aspect of Shiva; the Tryambakam mantra, alluding to Shiva's three eyes; and it is sometimes known as the Mrita-Sanjivini mantra because it is a component of the "life-restoring" practice given to the primordial sage Shukra after he had completed an exhausting period of austerity. The Maha Mrityunjaya mantra is hailed by the sages as the heart of the Veda. Along with the Gayatri mantra it holds the highest place among the many mantras used for contemplation and meditation

Word to Word Meaning of Maha Mrityunjaya Mantra

• ॐ aum = is a sacred/mystical syllable in Sanatan Dharma or Indian religions, i.e. Hinduism, Jainism, and Buddhism
• tryambakam = the three-eyed one (accusative case)
• yajāmahe = We worship, adore, honor, revere

• sugandhim = sweet smelling, fragrant (accusative case)
• puṣṭi = A well-nourished condition, thriving, prosperous, fullness of life
• vardhanam = One who nourishes, strengthens, causes to increase (in health, wealth, well-being); who gladdens, exhilarates, and restores health; a good gardener

• urvārukam = cucumber
  Cucumber
  The cucumber is a widely cultivated plant in the gourd family Cucurbitaceae, which includes squash, and in the same genus as the muskmelon. The plant is a creeping vine which bears cylindrical edible fruit when ripe. There are three main varieties of cucumber: "slicing", "pickling", and...
  
    (in the accusative case)
• iva = like, just as

URVAARUKIMIVA: 'URVA' means "VISHAL" or big and powerful or deadly. 'ARUKAM' means 'Disease'. Thus URVARUKA means deadly and overpowering diseases. (The CUCUMBER interpretation given in various places is also correct for the word URVARUKAM, but not apt for this mantra). The diseases are also of three kinds caused by the influence (in the negative) of the three Guna's and are ignorance (Avidya etc), falsehood (Asat etc as even though Vishnu is everywhere, we fail to perceive Him and are guided by our sight and other senses) and weaknesses (Shadripu etc. a constraint of this physical body and Shiva is all powerful).

• bandhanān = "from captivity" {i.e. from the stem of the cucumber
  Cucumber
  The cucumber is a widely cultivated plant in the gourd family Cucurbitaceae, which includes squash, and in the same genus as the muskmelon. The plant is a creeping vine which bears cylindrical edible fruit when ripe. There are three main varieties of cucumber: "slicing", "pickling", and...
  
  } (of the gourd); (the ending is actually long a then -d which changes to n/anusvara because of sandhi)

BANDANAAN means bound down. Thus read with URVAROOKIMIVA, it means 'I am bound down by deadly and overpowering diseases'.

• mṛtyor = From death
• mukṣīya= Free us, liberate us
• mā = not
• amṛtāt = [for] immortality, emancipation

Simple Translation

We hail the fragrant Three-eyed One who nourishes [all] and increases the [sweet] fullness of life.
As the cucumber

Cucumber

The cucumber is a widely cultivated plant in the gourd family Cucurbitaceae, which includes squash, and in the same genus as the muskmelon. The plant is a creeping vine which bears cylindrical edible fruit when ripe. There are three main varieties of cucumber: "slicing", "pickling", and...

is liberated from captivity [from its stem], may we [also] be liberated (mukshiya) from death (mrityor)not for the sake of immortality (maamritaat).
Actually OM is not spelled out in the Rig-Veda, but has to be added to the beginning of all Mantras as given in an earlier Mantra of the Rig-Veda addressed to Ganapati.
Om Tryambakam Yajamahe
th
Mrityor Mukshiiya Maamritat