You're probably fishing for "conductor".
Something that transfers thermal energy efficiently is called a conductor.
A good thermal conductor is something that transfers thermal energy efficiently. Materials like metals, such as copper and aluminum, are known for their ability to conduct heat effectively.
A material that transfers thermal energy efficiently is called a conductor. Conductors have high thermal conductivity, allowing heat to pass through them easily. This property is why materials like metal are often used in cooking pots and electrical wires.
An insulator
Thermal energy poorly and slowly transfers in liquids
The term for something that does not transfer thermal energy efficiently is "insulator." Insulators have low thermal conductivity and prevent the flow of heat from one area to another. Materials like wood, plastic, and rubber are commonly used as insulators.
Thermal gradient.
Radiation
Thermal energy can be transfered with three ways Conduction,Convection Radiation
stratosphere
convection
Conduction is the process that transfers thermal energy from the heating element to the bread in a toaster. The heating element gets hot and transfers heat directly to the bread through physical contact, causing the bread to toast.