The term SSSB (for small solar system body) is a classification
of solar system objects, consisting of
those smaller than dwarf planets. This includes all but the
largest minor planets (e.g., all but one asteroid) and
also all comets. Moons are not included. I'm not sure
whether it is meant to include meteoroids.
The term was officially coined in 2006 by the International Astronomical Union (IAU), as a more
general term than existing terms (such as "asteroid"), which are
often used with the intention of meaning a specific group of such
bodies,
such as those orbiting within a particular region of the
solar system.