1. noun /ˈklʌstə,ˈklʌstɚ/
A cluster of flowers grew in the pot.
b) A group of galaxies or stars that appear near each other.
The Pleiades cluster contains seven bright stars.
2. verb /ˈklʌstə,ˈklʌstɚ/
To form into a cluster.
The children clustered together around the puppy.
Wikipedia foundation.