1
general::
Repulse, drive away by blows, as in We tried to beat off the flying ants swarming about us. Originating in the mid-1600s in a military context, this term was being used for other activities by the mid-1700s.
American Heritage Idioms
2
general::
Phrase(s): beat someone or something off
to drive someone or something away by beating. • They beat the enemy off. • The army beat off the savage attack, saving the town. • I was able to beat off the intruder.
McGrawhill's American Idioms And Phrasal Verbs