A heat sword is a type of sword with its blade heated up to high temperatures to cause more damage to its target. This is often visualized as a sword with its blade glowing red hot from the heat.

If the blade starts catching on or covered in fire then it's now a flaming_sword.

Not to confused with

• energy_sword - The blade is made out of a solid opaque material (such as metal) and is not made out of energy or hardlight.