noun, noun which may take the genitive case particle 'no'
Refers to the side of a military formation or the side of the body. Often used in military contexts or anatomy.
敵軍の側背を突く作戦を立てた。
They devised a plan to attack the enemy's flank.
側背筋を鍛えるトレーニングをしている。
I'm doing exercises to strengthen my flank muscles.