お薄 is read as おうす (ousu) and means weak matcha.
おうす
ousu
けいはく
frivolous
てうす
insufficient (stock, money, etc.)
きはく
lacking (enthusiasm, consideration, substance, etc.)
にくはく
closing in on (the enemy, first place, etc.)
しなうす
shortage of stock
すすき
Japanese pampas grass (Miscanthus sinensis)
きのりうす
unenthusiastic
きたいうす
not to be depended on
じうす
thin (fabric, cloth, paper)
うすい
thin
うすぐらい
dim
うすぎ
being lightly dressed