slapdash adj. + Add to list US //ˈsɫæpˌdæʃ// UK //slˈæpdæʃ// slap·dash Informal SynonymsEtymology Synonyms bangbolthaphazardslam bangslapslipshodsloppysmackOrigin From slap + dash. First attested in the late 17th century, meaning "careless".