noun
midsummer; dog days of summer
In everyday use, 土用 almost always refers to the hottest period of summer, roughly late July through early August. Often associated with eating eel (土用の丑の日).
土用の丑の日にはうなぎを食べる習慣がある。
There is a custom of eating eel on the Day of the Ox during the midsummer period.
今年の土用は特に暑い。
This year's midsummer is especially hot.
noun
final 18 days of each season
Traditional calendar term: the last 18 days of each of the four seasons (spring, summer, autumn, winter). Rare in modern conversation except in set phrases or almanac contexts.
暦の上では、立秋の前の18日間が夏の土用にあたる。
On the traditional calendar, the 18 days before the start of autumn correspond to the summer 土用.