Thirteen year old Arvind Mahankali spelled the word "knaidel" to beat 11 other contestants and go on to win the high profile competition. However, Jewish linguists say that the preferred spelling is actually "kneydl," which refers to a small amount of unleavened bread, alternatively known as matzo balls.
The competition result will be upheld as the Spelling Bee uses Webster's Third New International Dictionary, published by Merriam-Webster, as the official spelling of all words used in competition.
Time details a little background information on the word:
"Yiddish, a language mashing Hebrew, German and Slavic roots, was once standard usage for Ashkenazic Jews. The Yiddish knaidel, written in Hebrew characters, was derived from the German knödel—which means the word went through three languages and two alphabets before making its way into an American-English dictionary."