From Wikipedia (granularity):
Granularity is the extent to which a
system is broken down into small
parts, either the system itself or its
description or observation. It is the
extent to which a larger entity is
subdivided. For example, a yard broken
into inches has finer granularity than
a yard broken into feet.Coarse-grained systems consist of
fewer, larger components than
fine-grained systems; a coarse-grained
description of a system regards large
subcomponents while a fine-grained
description regards smaller components
of which the larger ones are composed.