There are a variety of ways to define worship; here are a few of mine.

Encounter and Expression

Encounter: Meeting with God, seeing, who He is, understanding His attributes and character, what He does for you
(It is thanksgiving focused on the source.)

Expression: Celebrating what God has done, who God is based on your encounter with Him, acting on what God has done

Authentic worship is seeing God while looking life squarely in the face

Jeremiah 9:23-24 Thus says the Lord: “Let not the wise man boast in his wisdom, let not the mighty man boast in his might, let not the rich man boast in his riches, 24 but let him who boasts boast in this, that he understands and knows me, that I am the Lord who practices steadfast love, justice, and righteousness in the earth. For in these things I delight, declares the Lord.” (ESV)

Worship is a verb, it must be active. It is not simply knowing that God is great, but it is proclaiming it and acting on it so that God will be glorified.
Worship involves life actions not just words.

Worship is getting impressed by God

“What comes into our minds when we think about God is the most important thing about us.

The history of mankind will probably show that no people has ever risen above its religion, and man’s spiritual history will positively demonstrate that no religion has ever been greater than its idea of God. Worship is pure or base as the worshiper entertains high or low thoughts of God.

For this reason the gravest question before the Church is always God Himself, and the most portentous fact about any man is not what he at a given time may say or do, but what he in his deep heart conceives God to be like. We tend by a secret law of the soul to move toward our mental image of God. This is true not only of the individual Christian, but of the company of Christians that composes the Church. Always the most revealing thing about the Church is her idea of God.”

—A.W. Tozer, The Knowledge of the Holy (New York: HarperCollins, 1961), 1.

So what impresses you about God?

The deepest kind of transformation takes place in us when we become so deeply impressed with God and His purposes in and through our lives that our will, our volition, becomes engaged in the process of change and growth. (Richard E. Averbeck, © “Transforming Discipleship: Foundations of Christian Spiritual Formation.” Spiritual Formation Forum, May 19, 2004)