noun
kanji radical 大 when used as a crown (top component)
Refers specifically to the kanji component 大 when it appears at the top of a character, such as in 天, 夫, or 失. This is a technical term used in kanji dictionaries and calligraphy.
「天」の上の部分は大冠と呼ばれる。
The top part of 天 is called 大冠 (daikanmuri).
漢字辞典で大冠の部首を調べる。
I look up the radical 大冠 in a kanji dictionary.