A ghost usually (still) has the form of the body.
Giving up the ghost is translated from; to blow out, or exhale the soul/spirit,...
And crying with a loud voice, Jesus said, Father, "into Your hands I commit My spirit." And saying this, He breathed out the spirit. Lu 23:46 (Psa. 31:5) LIT
...or uncovered the soul, Nephesh.
He uncovered his soul in a violent death. (literally) Isa 53;12 (usually translated with "poured out his soul".)
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Anyway, what you get is a soul without a physical body; a ghost.
The concept of a ghost is well known in the Bible.
Then deep from the earth you shall speak, from low in the dust your words shall come; your voice shall come from the ground like the voice of a ghost, and your speech shall whisper out of the dust. Isa 29:4 RSV
But when the disciples saw him walking on the sea, they were terrified, saying,
"It is a ghost!" And they cried out for fear. Mt 14:26
RSV
Sometimes ghosts are conjured up.
And the woman said, Whom shall I bring up to you? And he said, Bring me up Samuel. And the woman saw Samuel, and cried with a loud voice. And the woman spoke to Saul, saying, Why have you deceived me? For you are Saul! And the king said to her, Do not be afraid. For what did you see? And the woman said to Saul, I saw gods (elohim; supernatural beings) coming up out of the earth. And he said to her, What is his form? And she said, An old man comes up, and he is covered with a cloak. And Saul saw that it was Samuel, and he bowed his face to the ground, and prostrated himself. And Samuel said to Saul, Why have you disturbed me, to bring me up? 1Sa 28;11 MKJV
This wasn't a demon, but, as the narrator confirms, it was Samuel.
The word ghost, like the German word Geist stem from older words like gest and gast which have the same root as geyser, and yeast, meaning; gushing with life. It is related to the even older word usgeisnan which has to do with ecstasy, (the state of mind.) or outer body experiences.
It is because of the ghost in it; the life-giving spirit, that a soul is called a ghost (or a spirit). Without this spirit, a ghost will vanish. Some ghosts have very little spirit (left) and can produce but fragmentary snapshotlike flickerings of moments that somehow were important to them in their past life.
The term also refers to the Rephaim, (Shades) the souls of the offspring of the fallen angels (Nephilim; fallen ones, plural for Nephil.). These giants (also called Nephilim) were drowned in the Flood after which their ghosts/souls would roam the earth as demons; evil spirits, looking for a place to stay.
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In general a ghost is a soul without a body. The term Holy Ghost however, always indicates the holy pneuma or ruach; the source; the force, or actually Holy Spirit; the life force of a soul. Cut of from this life force a ghost will eventually fade away, unless it finds a way to recharge.
In this remarkable paper, published in one of the most important medical/psychological journals, the author surveys the history of research into the survival of bodily death. He identifies three historical periods that mirror the scientific thinking of their times. At one point, research waned as many investigators believed that living individuals with paranormal powers were responsible for all the evidence. Now, however, research again proceeds on a broad front; even though hampered by most scientists' outspoken disbelief in the whole business.
The important types of evidence reviewed include the speaking of languages not normally learned, out-of-the-body experiences, and reincarnation memories. [Subjects that 99% of the scientific community would dismiss without examination. Ed.] The author, a professor of psychiatry, feels that this contempt is unwarranted and that most scientists are simply not aware of the vast amount of high quality data available. The long, well-documented paper concludes with the assertion that the data acquired so far do not actually compel the conclusion that life exists after death but that it certainly infers it strongly.
(Stevenson, Ian; "Research into the Evidence of Man's Survival after Death," Journal of Nervous and Mental Disease, 185:152, 1977.)