1. In sports, to disallow a goal due to a technical rule of the game. Primarily heard in UK. Their last-minute goal would have won the match, but it was chalked off due to an offsides ruling by the referee.

2. To record, mark, or make note of something, especially as having been completed. I always find it bittersweet to chalk off another birthday each year.

3. To delineate the border of something with chalk. You always see the police chalk off bodies of murder victims in movies. I wonder if they do that in real life.