This is the 903rd most frequent French word.
bras
Arm.
Here, 'bras' is used to mean the anatomical arm of a person.
Il a une blessure au bras.
He has an injury to his arm.
In this sentence, 'bras' refers to the region under the arm used for carrying.
Elle porte le sac sous son bras.
She carries the bag under her arm.
The phrase 'à bras le corps' uses 'bras' metaphorically to signify an action done with full engagement.