Thermal adhesive is a type of thermally conductive glue used for electronic components and heatsinks. Thermal adhesive is similar to thermal paste in that it is used for transferring heat from one surface to another. It is commonly used to bond heatsinks to motherboard chipsets and video card processors where there are no mounting holes to clamp a heatsink down.
The glue is usually a two-part epoxy resin.
Thermal adhesive is usually applied by the manufacturer of the part to which it is applied, although it is also sold to the general public.