a state of dreamy meditation or fanciful musing

lost in reverie.

a daydream.

a fantastic, visionary, or impractical idea

reveries that will never come to fruition.

Music . an instrumental composition of a vague and dreamy character.

noun

nightmare

noun

absent-mindedness , absorption , abstraction , castle-building , castles in the air , contemplation , detachment , dreaminess , dreaming , fantasy , fool’s paradise , head trip , inattention , meditation , mind trip , muse , musing , pensiveness , phantasy , pipe dream * , preoccupation , study , thought , trance , trip * , woolgathering , bemusement , brown study , daydreaming , daydream , fancy , fiction , figment , illusion , phantasm , phantasma , vision , dream , pipe dream