The proper meaning of this word is " perceptible by the senses " and a phenomenon is merely an occurrence that is perceptible by the senses. But these words have long been used by same writers as if they meant prodigious and prodigy. Mr. Vincent Crummles' daughter was called "the infant phenomenon" because she was, in her parents' opinion, a juvenile prodigy. This use has never been universally accepted, though it has respectable backing. It still gives some offence, and official writing should keep clear of it.