Simpai \Sim"pai\, n.[Malay simpei.] (Zo["o]l.) A long-tailed monkey ({Semnopitchecus melalophus}) native of Sumatra. It has a crest of black hair. The forehead and cheeks are fawn color, the upper parts tawny and red, the under parts white. Called also {black-crested monkey}, and {sinp[ae]}.