Two objects are in thermal contact if heat can flow between them. This can be done by making the two objects physically contact each other as when you put a cube of ice in a glass of warm water. Thermal contact can also be achieved without any physically contact as when you bring your hands near a fire, you feel the heat of the fire even though there is no physical contact between your hand and the fire.

Thermal contact and thermal equilibrium
3-2 The zeroth law of thermodynamics