1To penetrate deeply, or for a sensation or effect to sink in thoroughly.
真冬の寒さが体の芯まで徹するようだった。
The midwinter cold seemed to penetrate right to the bone.
彼の一言が胸に徹して忘れられない。
His single remark sank deep into my heart and I can't forget it.
2To devote oneself wholly to one thing, often used in the form ～に徹する (to be dedicated to ~).
彼は聞き役に徹して、あまり自分の意見を言わなかった。
He devoted himself entirely to the role of listener, and rarely voiced his own opinions.
監督は選手の育成に徹する方針を貫いた。
The manager stuck to a policy of devoting himself entirely to player development.
裏方に徹して、舞台を支え続けた。
He devoted himself entirely to working behind the scenes and kept supporting the production.
3To continue something without a break throughout a period of time, as in the phrase 夜を徹して (throughout the night).
徹夜という言葉のとおり、彼らは夜を徹して議論を続けた。
True to the word 徹夜 (all-nighter), they kept debating throughout the night.
締め切り前、夜を徹して原稿を仕上げた。
Before the deadline, I worked through the night to finish the manuscript.