Specter

Specter, also spelled spectre in British English, is a noun meaning a ghost or spirit, especially a visible haunting. It is also used metaphorically to denote a threatening presence or an unresolved possibility that continues to loom.

Etymology: The word derives from Middle English specter, from Latin spectrum through Old French spectre. The American spelling specter contrasts with the British spectre; both forms trace back to the Latin sense of appearance or image.

In culture and language, specters appear as haunted figures in folklore, fiction, and film. The term is common in phrases such as the specter of death or the spectral, used to describe ghostly or eerie phenomena.

In modern technology, Spectre (with capital S) is the name given to a class of security vulnerabilities in CPUs based on speculative execution. Publicly disclosed in 2018, Spectre describes variants that exploit speculative execution and indirect branch prediction. Mitigations have included software updates, changes to out-of-order execution behavior, and microcode updates to affected processors.

Notes: Specter and spectre are variant spellings primarily differing by regional convention; when used as a proper noun, such as in technical names, the capitalization and spelling may reflect branding or official naming. The term remains distinct from but etymologically related to other uses of “spectral” and “spectacle.”