make-believe contraption

noun
UK /ˈmeɪk bɪˌliːv kənˈtræpʃən/
US /ˈmeɪk bɪˌliːv kənˈtræpʃən/

A pretend machine that you imagine and build just for fun.

The kids built a make-believe contraption out of cardboard boxes and called it a spaceship.


OTHER MEANINGS

2. A complicated-looking device that seems real but does not actually work.

The prop department made a make-believe contraption that looked like a time machine.

3. A silly or overly complex plan that exists only in someone's imagination.

His scheme to clean his room with a make-believe contraption never worked.

4. A playful creation children pretend is a real machine during games.

She turned a laundry basket into a make-believe contraption for catching dragons.