An increase in rate of change.

Roget 274: velocity, speed, celerity; swiftness etc. adj.; rapidity, eagle speed; expedition etc. (activity) 682; pernicity^†; acceleration; haste etc. 684.    spurt, rush, dash, race, steeple chase; smart rate, lively rate, swift rate etc. adj.; rattling rate, spanking rate, strapping rate, smart pace, lively pace, swift pace, rattling pace, spanking pace, strapping pace; round pace; flying, flight.    lightning, greased lightning, light, electricity, wind; cannon ball, rocket, arrow, dart, hydrargyrum [Lat.], quicksilver; telegraph, express train; torrent.    eagle, antelope, courser, race horse, gazelle, greyhound, hare, doe, squirrel, camel bird, chickaree^†, chipmunk, hackee [U.S.], ostrich, scorcher [Slang].    Mercury, Ariel^†, Camilla^†, Harlequin.    [Measurement of velocity] log, log line; speedometer, odometer, tachometer, strobe, radar speed detector, radar trap, air speed gauge, wind sock, wind speed meter; pedometer.    ... show more

Roget 684: haste, urgency; despatch, dispatch; acceleration, spurt, spirt^†, forced march, rush, dash; speed, velocity etc. 274; precipitancy, precipitation, precipitousness etc. adj.; impetuosity; brusquerie^†; hurry, drive, scramble, bustle, fuss, fidget, flurry, flutter, splutter.    ... show more

Polish: akceleracja

The act of accelerating; increasing the speed.

synonyms: quickening, speedup.

Dutch: banketbakkersroom, versnelling
Polish: przyśpieszanie, przyspieszanie

physics A rate of increase of velocity.

Dutch: versnelling, acceleratie
Polish: przyśpieszenie, przyspieszenie