phantom

Etymology

From Middle English fantome, fanteme, from Old French fantosme, fantasme, from Latin phantasma (“an apparition, specter; (in Late Latin also) appearance, image”), from Ancient Greek φάντασμα (phántasma, “phantasm, an appearance, image, apparition, specter”), from φαντάζω (phantázō, “I make visible”). Doublet of phantasm.

noun

1. A ghost or apparition.
2. Something apparently seen, heard, or sensed, but having no physical reality; an image that appears only in the mind; an illusion or delusion.
3. (bridge) A placeholder for a pair of players when there are an odd number of pairs playing.
4. (medical imaging) A test object. A test phantom is an object that reproduces the characteristics of human tissue.

adj

1. Illusive.
   […] (it was the town's humour to be always gassing of phantom investors who were likely to come any moment and pay a thousand prices for everything) — “[…] Them rich fellers, they don't make no bad breaks with their money. […]” 1899, Stephen Crane, chapter 1, in Twelve O'Clock
2. Fictitious or nonexistent.
   a phantom limb