" light-mindedness "

1: a lack of seriousness often at an improper time;

  * e.g., " ... she displays a light-mindedness that might be excusable in a teenager but not in someone hoping to make it in the business world "

•  Synonyms : 

•  facetiousness,

•  flightiness,

•  flippancy,

•  frivolity,

•  frivolousness,

•  frothiness,

•  levity,

•  light-headedness,

•  lightness,

•  silliness

•  Antonyms : 

•  earnestness,

•  gravity,

•  seriousness,

•  soberness,

•  solemnity,

•  solemnness

1: lacking in seriousness or maturity;

  * e.g., " ... the movie was a light-minded take on the biblical story of Noah and the Flood "

•  Synonyms : 

•  birdbrained,

•  ditzy,

•  dizzy,

•  featherbrained,

•  flighty,

•  frivolous,

•  frothy,

•  futile,

•  giddy,

•  goofy,

•  harebrained,

•  light-headed,

•  puerile,

•  scatterbrained,

•  scatty,

•  silly,

•  yeasty

•  Antonyms : 

•  earnest,

•  serious,

•  serious-minded,

•  sober,

•  unfrivolous