Definition of "Superlative" :

noun: the superlative form of an adjective or adverb

"Fastest' is the superlative of the adjective fast'."

noun: an exaggerated expression (usually of praise)

"The critics lavished superlatives on it."

noun: the highest level or degree attainable; the highest stage of development

"So many highest superlatives achieved by man."

adjective: highest in quality