Shemini Atzereth
noun
She·mi·ni Atze·reth shə-ˈmē-nē-ät-ˈser-ət 
-əth,
-əs
: a Jewish festival following the seventh day of Sukkoth and marked by a special prayer for seasonal rain
Word History
Etymology
Late Hebrew shĕmīnī ʽăṣereth, from Hebrew shĕmīnī eighth + ʽăṣereth assembly
First Known Use
1868, in the meaning defined above