1A (typically wooden) bowl such as those used for soup; often referred to as 'o-wan'.
お椀を両手で持って飲む。
Hold the bowl with both hands and drink.
この椀は漆器でできている。
This bowl is made of lacquerware.
2A counter for bowls of food or drink (e.g., 'one bowl, two bowls').
味噌汁をお椀で二椀飲んだ。
I drank two bowls of miso soup.
彼女はご飯を一椀だけ残した。
She left only one bowl of rice.