accelerando UK /ætʃɛləˈɹændəʊ/US /ɑˌkʃɛl.əˈɹɑn.doʊ/noun 3adverb 1forms 2 noun3 •A tempo mark directing that a passage is to be played at an increasing speed. •Accelerating or exponential advancement or development (of a thing).The accelerando of the sciences and of technology, their mathematization have beggared both the reach and the veracity of natural language. — 2012 •A passage having this mark. adverb1 •With a gradual increase in speed. formsaccelerandoes · accelerandos