footwarmer
nounUK /ˈfʊtˌwɔːmə/
US /ˈfʊtˌwɔːrmər/
A footwarmer is a thing that keeps your feet warm.
She put her cold toes on the footwarmer under her desk.
OTHER MEANINGS
2. A small heated box or pan that people once placed their feet on in cold rooms.
In the old house, a brass footwarmer sat by the fireplace.
3. A person or animal that keeps someone's feet warm.
Her cat became a loyal footwarmer on winter nights.
4. A heated mat or pad used in a car or under a desk.
He plugged in the footwarmer during the long drive.