noun
crowding together; swarming; crowd; swarm
Describes a state where many people, animals, or things gather in a dense group. Often implies a disorderly or lively gathering.
駅前に人の群がりができていた。
A crowd of people had formed in front of the station.
夏の夜、灯りに虫の群がりが見える。
On summer nights, you can see swarms of insects around the light.
群れ is a more common word for a group or flock, often used for animals or people in a neutral sense. 群がり emphasizes the action or state of crowding together, sometimes with a nuance of disorder.
群がる is the verb form meaning 'to crowd around' or 'to swarm'. 群がり is the noun derived from it, referring to the resulting crowd or the act of swarming.
Noun form of the verb 群がる (mura-garu), which is derived from 群 (mura, 'group') + suffix がる (garu, 'to seem, to be inclined to'). The kanji 群 means 'crowd' or 'group'.