reverie

Short definition from Wiktionary

Noun

1. 1
   A state of dreaming while awake; a loose or irregular train of thought; musing or meditation; daydream.
2. 2
   An extravagant conceit of the imagination; a vision.
3. 3
   A caper, a frolic; merriment.

Verb

1. 1
   To daydream.