IPA: /ˈblækbɔːrd/
KK: /ˈblækˌbɔrd/
A flat, dark surface used in classrooms where teachers write with chalk.
The teacher wrote the math problems on the blackboard for the students to see.
Blackboard → The word is formed from "black" (from Old English "blæc", meaning dark or without light) and "board" (from Old English "bord", meaning a flat piece of wood or other material). A blackboard is a flat surface that is dark in color, typically used for writing on with chalk.
Think of a 'dark' surface ('black') that is a 'flat piece' ('board') used for writing. This helps you remember that a blackboard is a dark writing surface.