English Idioms and Idiomatic Expressions 

Body Idioms:  Brains
from: 'beat one's brains out'   to:  'wrap your brain around...'

• beat one's brains out
  • If someone beats their brains out, they try very hard to understand something or solve a problem.
    "My grandmother beats her brains out every evening trying to do the crossword puzzle in the newspaper."
    
    
• brain like a sieve
  • Someone who has a brain like a sieve has a very bad memory and forgets things easily.
    "Oh, I forgot to buy the bread - I've got a brain like a sieve these days!"
    
    
• all brawn and no brain
  • Someone who is physically very strong but not very intelligent is said to be all brawn and no brain.
    "He's an impressive player to watch, but he's all brawn and no brain."
    
    
• have something on the brain
  • If you have something on the brain, you think or talk about it all constantly.
    "Stop talking about golf. You've got golf on the brain!"
    
    
• (a) no-brainer
  • A decision or choice that requires little or no thought, because the best option is so obvious, is called a no-brainer.
    "The choice was between a cash refund or having the amount credited to my account - it was a no-brainer. I took the cash!"
    
    
• brains behind something
  • Someone who is the brains behind a project or action is the person thought to have planned and organised everything.
    "The police have arrested a man believed to be the brains behind the bank robbery."
    
    
• pick someone's brains
  • If you pick someone's brains, you ask questions about a particular subject in order to obtain advice or information.
    "Could we have lunch together? I'd like to pick your brains about something."
    
    
• rack one's brains
  • If you rack your brains, you try very hard to think of something or to remember something.
    "Christmas is always a hassle for me. I have to rack my brains every year to find ideas for presents."
    
    
• wrap your brain around something
  • If you concentrate on something in an effort to understand, you wrap your brain around it.
    "I need a translation of this report urgently, so wrap your brain around it fast!"