Compulsive preoccupation with a fixed idea or an unwanted feeling or emotion, often accompanied by symptoms of anxiety.(noun)
A compulsive, often unreasonable idea or emotion.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "obsession" in a sentence
"That is why the word obsession is a convenient one in the analytical vocabulary."
"People always use the word 'obsession' in a negative way, which I'm always amazed by."
"This obsession is aimless and brainless and ends with your oblivion in American politics."