humorous

if someone is brain dead, their mind is not working effectively, usually because they are very tired or very bored.

By the time I leave work I'm completely brain dead.

• a fashion victim
• a fast talker
• a fast track
• a fat cat
• a fate worse than death
• a fat lot of good
• a fat lot of use
• a faux pas
• a favourite son
• a feather in cap
• a feather in someone's cap
• a feather in your cap
• a feeding frenzy
• a feel for
• a feel for something
• a femme fatale
• a fender bender
• a few fries short of a Happy Meal
• a fifth wheel
• a fifty-fifty chance
• a fight for life
• a fighting chance
• a fig leaf
• a figment of imagination
• a figment of your imagination