To prostrate oneself in supplication on someone's grave/ pray at the grave of (a relative, saint, etc.)
He prayed to God near his grave. He held a memorial service in his memory near his grave.
("...And this is the taste of the house of Shammai. Then Rabbi Yehoshua went and prostrated himself on the graves of the house of Shammai, saying: I will answer you the strength of the house of Shammai, and its name is yours, thus - interpreted on one side as much and as much as" - Hagiga 22b)
Translation
Expression (Hebrew)
הִשְׁתַּטֵּחַ עַל קִבְרוֹ
Definition (Hebrew)
הִתְפַּלֵּל לָה' סָמוּךְ לְקִבְרוֹ. עָרַךְ טֶקֶס אַזְכָּרָה לְזִכְרוֹ בְּסָמוּךְ לְקִבְרוֹ.
("...וְזֶהוּ טַעְמָן שֶׁל בֵּית שַׁמַּאי. מִיָּד הָלַךְ רַבִּי יְהוֹשֻׁעַ וְנִשְׁתַּטַּח עַל קִבְרֵי בֵּית שַׁמַּאי, אָמַר: נַעֲנֵיתִי לָכֶם עַצְמוֹת בֵּית שַׁמַּאי, וּשְׁמָהּ סְתוּמוֹת שֶׁלָּכֶם כָּךְ- מְפֹרָשׁוֹת עַל אַחַת כַּמָּה וְכַמָּה"- חֲגִיגָה כב ע"ב)