What is the definition of “blade scatter” in gas turbine compressor dynamic balancing?

I assume there is an ellipsis somewhere in your source text, meaning the intended interpretation is "blade weight scatter", which does make sense in the context of dynamic balancing.

The meaning should be self-explanatory: the distribution of weights among nominally-equal turbo-machinery blades, which is important to keep the inertia tensor of the assembly as diagonal as possible when using the usual axis.