The takeoff rating is the maximum thrust that the engine is certified to produce.
This is generally specified for shout periods of time, (often 5 minutes) to be used only at takeoff.
For turbojet engines, the takeoff rating is specified as sea level static thrust (SLST).
There is a maximum ambient temperature for which the SLST can be maintained.
This is set by temperature limits for the internal engine parts.
The takeoff rating is generally used when sizing an engine for a new design.