Phasm refers to a ghost or apparition, but there are several other synonyms that can be used to describe it. One of them is specter, which is a ghostly image that appears to be terrifying or haunting. Another synonym is phantom, which refers to a supernatural being or ghostly entity that is often associated with a specific place or event. A wraith is another word that can be used instead of phasm, which represents a ghostly image or apparition that is believed to haunt a specific location. Finally, the word shade can be used synonymously with phasm, which is a ghost or apparition that is believed to be haunting but not malevolent in nature.