Dutch Etymology Compound of sluipen + moordenaar. Pronunciation IPA(key): /ˈslœy̯pˌmoːr.də.naːr/ Audio:(file) Hyphenation: sluip‧moorde‧naar Noun sluipmoordenaar m (plural sluipmoordenaars, feminine sluipmoordenares) assassin, furtive murderer (figurative) anything lethal that is hard to detectWikiwand - on Seamless Wikipedia browsing. On steroids.