An inflorescence (flower cluster) in which the central or terminal flower matures first; often flat-topped. An example from Hylotelephium spectabile is shown below.
Synonyms:
Cymes
Merriam-Webster Online Dictionary
cyme (noun) an inflorescence in which each floral axis terminates in a single flower , especially a determinate inflorescence of this type containing several flowers with the first-opening central flower terminating the main axis and subsequent flowers developing from lateral buds - see inflorescence illustration