warped shape; curved form
Describes an object that has become bent or warped out of its original shape, often due to heat, moisture, or pressure.
この板は反り形になっていて、まっすぐに置けない。
This board is warped and can't be placed flat.
Compound of 反り (そり, 'warp, curve') and 形 (かた, 'shape, form').