Corymbs are a type of inflorescence where the flowers are arranged in a flat-topped cluster. There are a few synonyms that can be used to describe this type of flower arrangement:
1. Umbels - a type of inflorescence where the flowers are arranged in a flat-topped cluster, but the stem comes from a single point (rather than each flower having its own stem).
2. Cymes - a type of flat-topped inflorescence where the central flowers bloom first and the outer flowers bloom later.
3. Panicles - a type of inflorescence that is more branched than a corymb, but still has a flat-topped shape.
Overall, corymbs are just one type of flower arrangement, and there are many other synonyms that can be used to describe similar formations.