What does "dust off" mean?
Restore to use. For example, I've dusted off last year's menu for the party. This usage alludes to cleaning and thereby renewing some object. [Mid-1900s]
Pitch a baseball dangerously close to the batter's head, as in I'm sure he dusted him off on purpose. [Slang; 1920s]
Finish off, kill; also, easily defeat. For example, They vowed to dust off the old man, or We'll dust off this team in no time. [Slang; c. 1940]
Thrash, beat up, as in If he didn't hand over his wallet, they threatened to dust him off. [Slang; 1920s]
Learn more about dust off