/sooh'peuhr gran'yeuh lay"sheuhn/ , Astron.
one of a number of large convection cells in the photosphere and chromosphere of the sun, each having a diameter of 10,000-20,000 mi. (16,000-32,000 km) and lasting longer than a day. Also called supergranulation .
[ 1970-75; SUPER- + GRANULATION ]