(sciences) Any spurious results clustered together, outside of normal expected ranges (as in a plot of recorded energy values, with an inexplicable blot, marring the clean expected results).

(linguistics) A fictitious or erroneous word, originally meaningless (not used in practice), that has been published in a dictionary or similarly authoritative reference work or otherwise listed as genuine, generally as the result of misinterpretation, misreading, or typographical error.

(photography) Any undesired image appearing at the image plane of an optical system; either a false image of the desired object, or an out-of-focus image of a bright source of light in the field of the optical system.

(computing) A copy of all the contents of a hard drive, used as a backup.

(Buddhism, Chinese folk religion) A type of supernatural being, condemned to desire more than it can consume. Often depicted with large belly and tiny mouth.

plural of grey ghost

(Canada) An unmarked police car or an unmarked vehicle used as a decoy by police.

Any of a group of frogs in the family Heleophrynidae, which live in mountain streams in South Africa.

(chromatography) a peak at an unexpected position (or time), due to e.g. contamination of the sample or from the previous analysis (if one of the substances had a retention time longer than the runtime)

(idiomatic, real estate) A residence intentionally kept vacant by an absentee owner, especially a foreign investor, as a financially safe asset to be liquidated at a convenient time.