The term SSSB (for small solar system body) is a classification of solar system objects orbiting the Sun, 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. It is not clear whether it is meant to include meteoroids.
The term was recently coined by the International Astronomical Union, 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.