群發

to send to multiple recipients / mass mailout / to occur in a clustered fashion

to send to multiple recipients; mass mailout / to occur in a clustered fashion

variant of 群[qun2]

group / crowd / flock, herd, pack etc

to send out / to show (one's feeling) / to issue / to develop / to make a bundle of money / classifier for gunshots (rounds)

cluster headache

earthquake swarm