Worship is an act of displaying devotion, paying homage, or offering reverence to God.
True worship is not meaningless ritual or a mindless, mechanical act but instead a heart-felt love and adoration to God, which is manifested in actions, be it by prayer, song, meditation, acts of service, and even through a lifestyle that honors him.
This may be best captured in John 4:23-24 which says we are to worship God in spirit and in truth.