brainteaser/ˈbɹeɪnˌtizɚ/EtymologyFrom brain + teaser.nounA problem or puzzle devised to exercise the brain and mind.“She bought me a book of brainteasers, which is both entertaining and also supposedly good for decreasing dementia risk.”Any difficult problem or puzzle.“Trying to figure out how to square this circle is a brainteaser to say the least.”