noun, noun which may take the genitive case particle 'no'
Refers to something being of a large size, often used in product descriptions or when specifying dimensions.
このTシャツの大サイズはありますか？
Do you have this T-shirt in a large size?
大サイズのスーツケースを買った。
I bought a large-sized suitcase.
Compound of 大 (だい, 'large') and サイズ (saizu, 'size'), a straightforward combination of a Sino-Japanese prefix and an English loanword.