A group of sheep, goats, or birds. (Cambridge Dictionary)
A large group of people, usually people of a particular type. (Cambridge Dictionary)
A number of birds of one kind feeding, resting, or travelling together. (Oxford Dictionaries)
A number of domestic animals, especially sheep, goats, or geese, that are kept together. (Oxford Dictionaries)
A large number or crowd of people. (Oxford Dictionaries)
A group of animals (such as birds or sheep) assembled or herded together. (Merriam – Webster)
A group under the guidance of a leader. (Merriam – Webster)
A large number. (Merriam – Webster)
Flock of birds, sheep, or goats is a group of them. (Collins Dictionary)
You can refer to a group of people or things as a flock of them to emphasise that there are a lot of them. (Collins Dictionary)
If people flock to a particular place or event, a very large number of them go there, usually because it is pleasant or interesting. (Collins Dictionary)
Examples
Why Do Birds Flock?
https://www.thespruce.com/what-does-a-flock-of-birds-mean-386452
Flock. Wiktionary.