A thinner, more dilute form of matcha (usucha) used in the tea ceremony; easier to drink than koicha.
今日は気軽に飲めるようにお薄を頼んだ。
Today I ordered usucha so it would be easy to drink.
茶会の最後にお薄が出されることが多い。
At tea gatherings, usucha is often served at the end.