2. Any activity requiring concentration that is so mind-numbingly repetitive that your ability to think is adversely affected (see also above)
3. A proposition so wild, implausible or difficult that it defies comprehension. Precedes a Brain Tilt
4. A (supposedly) very difficult puzzle, riddle or problem
Doing a tax return can rapidly become a brainscrambler
The global warming debate is a real brainscrambler.
Thinking about you sleeping with me is a brainscrambler.
Radio "Win a free X by solving this afternoon's brainscrambler"