'Solemn' in the Bible

I will also cause all her mirth to cease, her feasts, her new moons, and her sabbaths, and all her solemn assemblies.

What will ye do in the day of solemn assembly, and in the day of the feast of Jehovah?

But I am Jehovah thy God from the land of Egypt; I will yet again make thee to dwell in tents, as in the days of the solemn feast.