He extended his neck to the slaughter, he bared his neck to the slaughter
In the question: He went to his death without resistance. He did not fight for his life. He shared in the action with the one who came to kill him.
("Rise up, my flock, from exile, for the sake of Abraham, the law and the sister of me, my brother, for the sake of Isaac, who was able to do his work and who stripped his robe to slaughter for my name, and for me, for the sake of Jacob" - Pesikta Zutrata (Take Good) Shemot Chapter 12, and also: "Izhak, who stripped his robe to slaughter" - Otzar Hamidrashim (Eisenstein) Psyche, 489)
Translation
Expression (Hebrew)
הוֹשִׁיט אֶת צַוָּארוֹ לִשְׁחִיטָה, פָּשַׁט צַוָּארוֹ לִשְׁחִיטָה
Definition (Hebrew)
בְּהַשְׁאָלָה: הָלַךְ לָמוּת לְלֹא הִתְנַגְּדוּת. לֹא נִלְחָם עַל חַיָּיו. שִׁתֵּף פְּעֻלָּה עִם זֶה שֶׁבָּא לַהֲרֹג אוֹתוֹ.
("קוּמִי לָךְ, מִן הַגָּלוּת, רַעְיָתִי, בִּזְכוּת אַבְרָהָם שַׁרִיעַה וְאִחָה אוֹתִי, יָפָתִי, בִּזְכוּת יִצְחָק שִׁיְּפָה מַעֲשָׂיו וּפָשַׁט צַוָּארוֹ לִשְׁחִיטָה עַל שְׁמִי, וּלְכִי לָךְ, בִּזְכוּת יַעֲקֹב"-פְּסִיקְתָּא זוֹטְרָתָא (לֶקַח טוֹב) שְׁמוֹת פֶּרֶק יב, וְכֵן:" יִצְחָק שֶׁהוֹשִׁיט צַוָּארוֹ לִשְׁחִיטָה"-אוֹצַר הַמִּדְרָשִׁים (אַיְזֶנְשְׁטֵיְן) פְּסִיקְתָּא,489)