Spectres are ghosts or spirits of dead people.
Spectres are often thought of as scary or spooky.
Examples:
The old house is haunted by spectres.
I saw a spectre in the graveyard last night.
The spectre floated through the wall.
The spectre moaned and rattled chains.
The spectre's eyes glowed in the dark.
The children told stories about the spectres in the forest.