Daydream (noun)

A series of pleasant thoughts or fantasies that distract one from reality, often occurring during periods of idleness or boredom.

Origin:

Day + dream, a dream or a series of thoughts or images that occur during the day while one is awake.

Examples:

1. She was lost in a daydream and didn't hear the teacher calling her name.
2. He daydreamed about winning the lottery and buying a big house.
3. She daydreamed about a vacation in a tropical paradise.
4. He daydreamed about being a famous actor.
5. She daydreamed about a life without any responsibilities.