The phrase "grim ghost" describes a spirit that is haunting, frightening, or sorrowful. Some synonyms for this phrase include "spectral shade," "ghastly apparition," "eerie entity," and "haunted phantasm." Other options include "spooky specter," "terrifying wraith," and "fearsome revenant." Each of these synonyms suggests a different nuance of the original phrase, from spooky and mysterious to ominous and chilling. Whether describing the ghost of a loved one or a malevolent spirit, these synonyms offer a range of ways to evoke the eerie presence of the supernatural.