What is the meaning of Solemnity?

The quality of being deeply serious and sober or solemn.

An instance or example of solemn behavior; a rite or ceremony performed with reverence.

A feast day of the highest rank celebrating a mystery of faith such as the Trinity, an event in the life of Jesus, the Virgin Mary, or another important saint.

A solemn or formal observance; proceeding according to due form; the formality which is necessary to render a thing done valid.

A celebration or festivity.

Source: wiktionary.org