To make ghostly or ghost-like in appearance or quality; to give something a spectral or eerie character.
From 'ghostly' + '-ify' suffix (meaning to make or cause to be). A constructed verb following productive English word-formation patterns.
The '-ify' suffix can attach to almost any adjective to create a verb—'ghostlify' means 'to make ghostly,' just as 'clarify' means 'to make clear'—this is why English speakers can understand newly invented words they've never heard before.
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