Related Clues:

• Demagnetized, perhaps
• Wiped away
• Wiped the slate clean
• No longer on the board
• Rubbed
• Got rid of marks
• Cleared the board
• Cleaned, as a blackboard
• Cleaned with a cloth
• Helped with the blackboard
• Totally beat
• Bleeped out
• Wiped off
• Off the board
• No longer on tape