Wiktionary
bathful
n. As much as a bath will hold.
Usage examples of "bathful".
I prefer to arrive in New York at night, to lower myself into the city gradually, like getting into a bathful of very hot water.
However, do not add more than three drops of peppermint, lemon or Cedarwood, and no more than four or five drops of other astringent or potent oils such as orange, pine, rosemary, tea tree and thyme to a bathful of water and follow instructions carefully.