be/live in a dream world

to have ideas or hopes which are not practical and are not likely to be successful.

If she thinks he's suddenly going to turn into the perfect boyfriend, she's living in a dream world. (usually in continuous tenses)

• in awe of someone
• in awe of something
• in a word
• in bad faith
• in bed with
• in bed with someone
• in birthday suit
• in black and white
• in blood
• in brief
• in broad daylight
• in broad strokes
• in cahoots
• in cahoots with
• in cahoots with someone
• in case
• in case of
• in case of something
• in charge
• in charge of
• in charge of something
• in check
• in chorus
• in close quarters
• in cold blood