Gothic novel is a novel in which supernatural horrors pervade the action.
The setting:
sinister humans, mysterious castle with secret passages
Gothic elements:
ghosts, portents, devils, haunted apparitions, skeletons, omens, ancient prophecy, obscure or hard to understand events, sentimentalism, supernatural events, imprisoned characters and terror fight
Gothic novel examples:
Daphne du Maurier, Rebecca
Horace Walpole, The Castle of Otranto
Mary Shelley, Frankenstein
William Beckford, Vathek
Anne Radcliffe, The Mysteries of Udolpho