also: ひょうちん
noun
ice pillow; cooling pillow
A pillow-like device, often made of rubber, filled with ice or cold water and used to cool the head or body, especially for fever or heat.
熱があるので、氷枕をして寝ます。
I have a fever, so I'll sleep with an ice pillow.
夏は氷枕を使うとよく眠れます。
In summer, using an ice pillow helps me sleep well.