Definition #1: A public work done for the service of others.
The work of liturgy is public, not private. Mass is not a time for private prayer. It is the intention of the Church that we come together as a faith-filled community and publicly worship God.
Liturgy is work -
Who does the work? Just the priest or the really holy people in the front pew? No! Everybody is called to work at the liturgies. We are all the ministers of hospitality as we greet each other in community; we are all
ministers of Holy Communion as we receive Jesus in sacrament; we are all involved in the Liturgy of the Word as we listen and respond to the Gopspel and readings.
Liturgy is done for the service of others -
When we all come together and actively work in this paschal mystery, God can take our broken lives in the "broken bread" and turn them into the resurrected Body of His Son for our good and the good of all His people. Christ was anointed Priest, Profit and King, so may we all live as members of His body. By Baptism, we shall share in the priesthood of Christ, in His prophetic and royal mission. Liturgy is a public work done for the service of others.
Liturgy is the faith of the community in motion -
Definition #2: A sacred action by which the priestly work of Christ is made present and effective
in the lives of the faithful.
What is the priestly work of Christ? -
Reconciliation between God and man, and between man and man. Liturgy is not one work of the Church, but THE WORK of the Church.
There is a primacy to liturgy and to what we do in liturgy. If we look at the history of the Church, we see that people did not wait for liturgical rites to be written down before they learned how to worship. Remember, the Eucharist was celebrated some 20 years before St. Paul ever wrote about it! Liturgy is the faith of the community in motion.
Liturgy is the Foretaste of the Eternal Banquet -
"In the earthly liturgy, we share in the foretaste of that heavenly liturgy which is celebrated in the Holy City of Jerusalem toward which we journey as pilgrims, where Christ is sitting at the right hand of God, Minister of the sanctuary and of the true tabernacle. With all the warriors of the heavenly army we sing a hymn of glory to the Lord; venerating the memory of the saints, we hope for some part and fellowship with them; we eagerly await the Savior, our Lord Jesus Christ, until he, our life, shall appear and we too will appear with him in glory."
- Catechism of the Catholic Church #1090