サーモインナー

noun

thermo inner; thermally molded inner lining

A specialized term used in sports equipment, especially ski boots, referring to an inner boot that is heat-molded to the wearer's foot for a custom fit.

• 新あたらしいスキーブーツのサーモインナーを足あしに合あわせて成せい形けいした。

  I molded the thermo inner of my new ski boots to fit my feet.