彼の新しいビジネスは大成功だった。
His new business was a great success.
prefix
Used in family or hierarchical terms to indicate seniority, e.g., 大おじ (great-uncle), 大先輩 (senior superior).
大おじが昨日亡くなった。
My great-uncle passed away yesterday.
prefix
Used in words like 大詰め (final stage) or 大一番 (decisive match) to indicate the last or most critical part.
交渉は大詰めを迎えている。
The negotiations are reaching the final stage.
prefix
Indicates something approximate or not detailed, as in 大ざっぱ (rough, approximate) or 大まか (broad, general).
大ざっぱな見積もりを出してください。
Please give a rough estimate.
The reading だい is more common in Sino-Japanese compounds (e.g., 大学, 大丈夫), while おお is used in native Japanese words and some compounds.
Native Japanese prefix related to the adjective 大きい (おおきい, 'big'). The reading おお is the older form, while だい is the Sino-Japanese reading.