brain cell

noun3

1. •
   A cell in the brain, such as a neuron or a glial cell.
2. •
   (informal) A neuron.

   • Did you know that you have brain cells in your stomach? — 2018
3. •
   (humorous, figurative) Taken as a unit of intelligence, especially in small quantities.

   • Those two morons only have one brain cell to share between them.