側そく背はい

noun, noun which may take the genitive case particle 'no'

flank

Refers to the side of a military formation or the side of the body. Often used in military contexts or anatomy.

• 敵てき軍ぐんの側そく背はいを突つく作さく戦せんを立たてた。

  They devised a plan to attack the enemy's flank.

• 側そく背はい筋きんを鍛きたえるトレーニングをしている。

  I'm doing exercises to strengthen my flank muscles.