PRESTISSIMO
prestissimo
(adjective) (of tempo) as fast as possible
prestissimo
(adverb) extremely fast; as fast as possible; “this passage should be played prestissimo”
Source: WordNet® 3.1
Etymology
Adjective
prestissimo (not comparable)
(music) Extremely fast, the fastest possible tempo. [from 18th c.]
Adverb
prestissimo (not comparable)
(chiefly music) Very quickly. [from 19th c.]
Source: Wiktionary
Pres*tis"si*mo, adv. Etym: [It., superl. of presto.] (Mus.)
Definition: Very quickly; with great rapidity.
Source: Webster’s Unabridged Dictionary 1913 Edition