bugaboo

noun

1. an imaginary monster used to frighten children

   noun.person

   Synonyms bogeyman booger boogeyman bugbear

   Source: WordNet 3.0

2. a source of concern

   noun.cognition

   Examples

   The old bugaboo of inflation still bothers them.

   Source: WordNet 3.0

3. Something frightful, as a specter; anything imaginary that causes needless fright; something used to excite needless fear; also, something really dangerous, used to frighten children, etc.

   noun

   Source: webster1913