犀 is a bound form (b.f.) — it cannot stand alone as an independent word in modern Chinese. You'll always find it inside a compound, most commonly 犀牛 'rhinoceros' and 犀利 'sharp, incisive (of speech or writing)'. The gloss 'rhinoceros' is accurate for the character's core meaning, but trying to use 犀 by itself would sound incomplete; always pair it with 牛 for the animal.