1The jaw or chin; the bony structure at the lower part of the face used for chewing and speaking, including both the upper and lower jaw.
転んで顎を強く打ってしまった。
I fell and hit my jaw hard.
彼はがっしりした顎をしている。
He has a strong, well-defined jaw.
あごに手を当てて考え込んだ。
He put his hand on his chin and fell into thought.
長時間話し続けて、あごが疲れた。
My jaw got tired from talking for so long.
彼女はあごのラインが美しい。
She has a beautiful jawline.
2The barb of a fishhook — the small backward-pointing projection near the tip that keeps a caught fish from slipping off. A specialized fishing term.
釣り針の顎が折れていたので、魚に逃げられてしまった。
The barb on the hook was broken, so the fish got away.
キャッチ＆リリース用には、あごのない針を使うとよい。
For catch and release, it's best to use barbless hooks.