This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. Compulsive preoccupation with a fixed idea or an unwanted feeling or emotion, often accompanied by symptoms of anxiety.

n. A compulsive, often unreasonable idea or emotion.

n. A compulsive or irrational preoccupation.

n. An unhealthy fixation.

n. The act of besieging.

n. The state of being besieged; -- used specifically of a person beset by a spirit from without.

n. An excessive preoccupation of the thoughts or feelings; the persistent haunting or domination of the mind by a particular desire, idea, or image.

n. Any driving motive; a compelling goal; -- not necessarily implying a negative judgment, as does sense 3

n. Something that causes an obsession{3}.

n. The state of being obsessed.

n. The act of besieging; persistent assault.

n. Continuous or persevering effort supposed to be made by an evil spirit to obtain mastery of a person; the state or condition of a person so vexed or beset: distinguished from possession, or control by a demon from within.

n. In pathology, a constant brooding upon any subject, such as the thought of death, until the mind becomes dominated by that one idea.

n. an unhealthy and compulsive preoccupation with something or someone

n. an irrational motive for performing trivial or repetitive actions, even against your will

"That is why the word obsession is a convenient one in the analytical vocabulary."

preoccupation   

obsess    obsessively    obsessed    obsessive    obsessional   

Hessian    accession    aggression    compression    concession    confession    decompression    depression    digression    discretion   

urge    compulsion    delusion    fascination    aversion    hallucination    fantasy    hysteria    paranoia    preoccupation