noun
upright-floating tea stalk (lucky omen)
A tea stalk that floats vertically in one's cup, traditionally considered a sign of good luck.
今日のお茶に茶柱が立っていた。
A tea stalk was floating upright in my tea today.
茶柱が立つと、いいことがあると言われている。
They say that when a tea stalk stands upright, something good will happen.