in swarms; in great crowds; in huge numbers
Describes people, animals, or things appearing or gathering in large, often lively numbers. Colloquial and somewhat emphatic.
People had gathered in swarms at the festival.
Used for an abundant amount of something, often with a sense of overflowing or more than enough. Can be used for both countable and uncountable things.
Tomatoes are growing plentifully in the field.