side (of the torso); flank
illegitimate child; child born by someone other than one's wife
脇腹に痛みを感じた。
I felt a pain in my side.
転んで脇腹を強く打った。
I fell and hit my side hard.
脇腹の筋肉を鍛えるには腹筋運動が効果的だ。
Abdominal exercises are effective for training the muscles in the flank.