obsession Meaning, Definition & Usage

  1. noun an irrational motive for performing trivial or repetitive actions, even against your will
    compulsion.
    • her compulsion to wash her hands repeatedly
  2. noun an unhealthy and compulsive preoccupation with something or someone
    fixation.

WordNet

Ob*ses"sion noun
Etymology
L. obsessio: cf.F. obsession.
Definitions
  1. The act of besieging. Johnson.
  2. The state of being besieged; -- used specifically of a person beset by a spirit from without. Tylor.
    Whether by obsession or possession, I will not determine. Burton.

Webster 1913