I think worship is actually pretty hard to define, but I'll see if I can offer some thoughts.
In one sense worship is that which affirms and declares God worthy of our highest praise, our thankfulness, of our faith, of our submission and obedience, of our utmost adoration.
We do this by affirming, and living, recognizing that He alone is God and there is no other. Necessarily that means that nothing else can be divine, and nothing else can take the place in our lives or even come close to rivaling the place of God. "You shall have no other gods before Me" means not only are we to abstain from the worship of false gods, such as the various pagan gods of ancient polytheistic religions; but nothing can have that priority, nothing can have that importance. In his Large Catechism Martin Luther wrote:
"That now, I say, upon which you set your heart and put your trust is properly your god. ... to have a god is to have something in which the heart entirely trusts." - The Large Catechism, Section I, The First Commandment
Faith, here, we might also call confidence; a radical and bold trust which clings and cleaves. For St. James reminds us, "even the demons believe, and tremble"; it is hardly sufficient to simply believe, or know, that there is only one God, and that He who is unveiled as the God of Abraham, of Isaac, and of Jacob; the God of Israel, the God of the Prophets; to know that indeed He is the God and Father of Jesus Christ--the devils know all this better than even we do.
It is therefore faith of a different sort, not mere belief, or knowledge; but trust, confidence, clinging; it is to have this God as your God. The One in whom you trust, the One you confide in, the One you hold dearest and nearest. That which is your refuge, that which is your safety.
That He is your Father, and your King, and your Lord, and your Friend. And that He is these things, and you can trust in Him, and believe in Him, and come to Him, and confide in Him. To be feared, yes, to be adored, yes; to be loved. "You shall love the Lord your God with all your heart, with all your soul, with all your strength, and with all your mind"
In Deuteronomy 6:5, which the Lord quoted in the Gospels, the word translated as "might" (rendered as "strength" in the Gospel texts) is me'od, it's not a noun, but an adjective, it means exceedingly, greatly, and much. As in when, in Genesis, God declares all that He made me'od tov, "exceedingly good". To love God with all our exceedingly, all of our much. With all our lebab, our inward parts, our heart and mind, the core of who and what we are; with all of our nephesh, our life, our breath; and also with all our me'od--with much, with our exceedingly--with everything else, with everything. Our innermost, our whole life, our utmost.
God is to be the object of our innermost, our whole life, our utmost.
In our minds, in our hearts, and in everything we do, think, say, feel, and are.
St. John does remind us, "We love because He first loved us", so let's not imagine that this love of God comes naturally, or easily, or can happen because of our mere striving. It can't, as St. Paul reminds us that all have sinned, all have fallen short, all have gone astray, there is none who is righteous, none who does good, none who loves or seeks God--all are sinful, all have betrayed our Creator, all have succumbed to myriad idolatries, all have become perverse--all are deserving of death and hell.
But God, rich in mercy, meets us not in what we deserve; but meets us in His grace, meeting us in Jesus Christ. God sees our hate, and responds in love, with love, holding us dear. And His love, His mercy, His goodness turns these broken stoney hearts into soft, clean, restored, healed hearts of flesh that learn to beat in rhythm to His love. As we abide in Jesus, trusting in Christ, abiding in His word, abiding in His Sacraments. The Holy Spirit, in us, healing us, sanctifying us, making us children of the Father, joint-heirs with Jesus Christ Himself. To call God Abba, Father. To love Him, for He loved us. To know Him, as He knows us. To have Him, as He has us.
So worship begins with this, God created us in His image. To reflect, to bear, to have communion and intimacy with Himself. That is, to be human. Lost and broken by sin and death and held in bondage by the devil; set free, healed, restored, and saved in and by and through Jesus Christ who suffered, died, and rose again (and who is coming again). To be restored to communion, to come to God, as a lost child to a most loving Father. For in Christ, by the Spirit, we are children of the Father.
Worship continues, as we abide by faith in Christ, in His word and in His Sacraments. To hear and receive that good which God freely gives as grace. To offer the sacrifice of praise, to adore and love and thank Him for all He has done. To love our neighbor as ourselves, and freely and humbly submit ourselves in obedience to the will and way of God. To be holy even as He is holy. To be merciful, to forgive even as we have been forgiven. To do justice and to love kindness, to walk humbly with our God. To love even as He has loved us; to love Him, and to love our neighbor.
In the Liturgy this worship is expressed in a wonderful way, for here God meets us in Word and Sacrament, loving us, healing us, justifying us, sanctifying us, saving us. And we, the People of God, mirroring what is revealed from heaven, and in anticipation of the Marriage Feast that is to come, offer thanks, and praise, and join the angels and holy saints who came before us in saying Holy, Holy, Holy. In songs, and psalms, and prayers. We hear, and we believe, we offer thanks, and we pray, we praise and rejoice, celebrating with joy the gifts and goodness of our God.
But it is not the individual elements--the music, the individual prayers, etc which are worship. These are expressions of worship. Worship is what it means to be created in the image of God, to have that image restored and being restored; and to live as children of our Father, in imitation of Christ, by the power of the Spirit who lives in us. To have faith, to abide, to obey. In our innermost, in our whole life, in our utmost. A worshiping people sing, but the song is not worship, it is worship which causes us to sing, which wells from within us, springs up from and bubbles and overflows to the surface as Hallelujah in not just our song, and words, and prayers, but in our actions, in our thoughts, in our dealings with others.
-CryptoLutheran