Ghulūw pushes a description into what is rationally impossible, and hence also impossible as ordinary occurrence. The claim exceeds not only experience but the conceptual conditions for its realization.
For example, one might describe a terrifying figure as frightening beings that do not yet exist. Fear is extended beyond presently existing subjects in a way that literal assertion cannot sustain.
The definition of ghulūw does not itself settle whether its use is rhetorically rejected. Under qualifying literary conditions, even ghulūw may be acceptable.