スピードダウン LinksSentence search for スピードダウンSentence search for スピード・ダウンEdit in JMdict Noun, Suru verb, Intransitive verb, Transitive verb1. slowing downWasei, word made in Japan, From English “speed down”. Wasei (word made in Japan)Other formsスピード・ダウン Discussions Log in to talk about this word.