The biblical and Orthodox understanding of Tradition should be considered in a different category than what many of the above posts describe, not at all incorrectly, as traditionalism. Holy Tradition as it is understood in the Eastern Church is congruent to but not reducible to such phenomena.
The Greek word and its cognates refer to something that is handed down or delivered/received. Some examples:
1 Cor 11:2: I commend you because you remember me in everything and hold firmly to the traditions, just as I delivered ["traditioned"] them to you.
1 Cor 11:23: For I received from the Lord that which I also delivered to you, that the Lord Jesus in the night in which He was betrayed took bread
2 Thess 2:15: So then, brethren, stand firm and hold to the traditions which you were taught, whether by word of mouth or by letter from us.
2 Thess 3:6: "keep away from every brother who is idle and does not live according to the teaching you received from us."
Gal 1:14: "I was advancing in Judaism beyond many of my contemporaries among my countrymen, being more extremely zealous for my ancestral traditions."
All major contemporary scholars would concur with the proposition tradition (apostolic tradition) existed prior to the composition of any New Testament book (e.g. 1 Cor 11:23; there are many examples in the NT and the relevant academic literature).
Although Protestantism and Roman Catholicism have historically discussed tradition as a separate category from scripture, Orthodox regard scripture as an *example* of tradition -something handed down- as was also common in the early fathers (e.g. Clement of Alexandria uses the phrase "as the scripture traditioned" G. L. Prestige, Fathers and Heretics, pp. 13f. citing strom I.21, 142.2, 7.18, 109.2).
This is quite in accord with NT usage which speaks of the Gospel itself as "traditioned":
1 Cor 15:1 Now I make known to you, brethren, the gospel which I preached to you, which also you received, in which also you stand,
Gal 1:9 As we have said before, so I say again now, if any man is preaching to you a gospel contrary to what you received, he is to be accursed!
Cf. 1 Clem 42: "The message was delivered orally by our Lord to the apostles and was handed on orally by them to their successors."
There is, I think, a disparity between the paleo-orthodox view of tradition as something handed down and the Roman Catholic idea of tradition as something quite specifically located in the papal office, in the manner Pope Pius IX reflected when he said "I am Tradition"; cf. also Jaraslov Pelikan's statement "Pope Pius did not attempt to prove that the doctrine of the assumption was taught as such in scripture or confessed in the earliest documentary witnesses to the Christian and Catholic faith. Instead, he attached his promulgation of the dogma to the development of a tradition for which there is admittedly no authentic witness... among the Fathers of either the East or the West prior to the end of the fifth century" (Jaroslav Pelikan, Development of Christian Doctrine: Some Historical Prolegomenna (Yale, 1979), p. 38).
What is meant by Holy Tradition in Orthodox understanding is more than simply texts and teaching in a secular sense, incorporating the actual message, right worship, right prayer, and so on, not in the sense of hermeneutics, exegesis, and/or historical analysis (albeit not necessarily severed from such things by any means) but in the sense of theoria, which is to say that only those who live the Word through the Holy Spirit can know the Word and be receptacles or vehicles of Holy Tradition -as opposed to "mere traditions":
"Byzantines... presupposed a concept of Revelation which was substantially different from that held in the West. Because the concept of theologia in Byzantium ...was inseparable from theoria ("contemplation"), theology could not be -as it was in the West- a rational deduction from 'revealed' premises, i.e. from Scripture or from the statements of an ecclesiastical magisterium... Not that a rational deductive process was completely eliminated from theological thought, but it represented for the Byzantines the lowest and least reliable level of theology. The true theologian was the one who saw and experienced the content of theology; and this experience was considered to belong not to the intellect alone ...but to the 'eyes of the Spirit,' which place the whole man -intellect, emotions, and even sense- in contact with divine existence" (John Meyendorff, Byzantine Theology, pp. 8f.).
"Theoria is a 'spiritual perception of the one sent by God.. possible only to the believer' ("Theorao" in Arnt and Gingrich, eds., A Greek-English Lexicon of the New Testament and Early Christian Literature, 1b). It is an insight into God's Word that cannot be received by one who is a 'fleshly' Christian, one whose diet consists of only milk, not meat (1 Cor 3:1-2). This one's spiritual senses will e numbed and handicapped (1 Cor 2:14) and will never be able to have his senses fine-tuned so as to discern Good and evil (Heb 5:13-14). The one with a theoritic vision has a heart trained to see Truth, a heart transformed by the Spirit toward purity and godliness. 'Blessed are the pure in heart for they shall see God' (Matt 5:8)" (cf. Jordan Bajis, Common Ground: An Introduction to Eastern Christianity for the American Christian, ch 7).
"The pure notion of Tradition can then be defined by saying that it is the life of the Holy Spirit in the Church, communicating to each member of the Body of Christ the faculty of hearing, of receiving, of knowing the Truth in the Light which belongs to it" -Vladimir Lossky, In the Image and Likeness of God, p. 152).