潜入せんにゅう Common Noun Irregular Intransitive English jmdict 1 noun (common) (futsuumeishi) noun or participle which takes the aux. verb suru intransitive verb infiltration;sneaking in;going undercover 彼は農夫に身をやつして城下町に潜入した。 Disguising himself as a peasant, he crept into the castle town.