: any of a family (Rhinocerotidae) of large heavyset herbivorous perissodactyl mammals of Africa and Asia that have one or two upright keratinous horns on the snout and thick gray to brown skin with little hair.See rhinoceros defined for English-language learners.See rhinoceros defined for kids.ord History of RHINOCEROS. The ancient Greeks were familiar with the African species of rhinoceros and called the animal in Greek monokerōs, “ one-horned, ” and more commonly rhinokerōs, “ nose-horned.