A speaker may mentally compare one entity with another while omitting an explicit mention of the vehicle. The named subject is accompanied by a feature that normally belongs to the omitted vehicle.
Under a standard rhetorical analysis, this is called implicit metaphor (istiʿārah makniyyah). The omitted vehicle is suggested by mentioning one of its characteristic attributes.
The subject, the absent vehicle, its accompanying attribute, and the clue to the intended sense should be kept distinct; rhetorical authorities differ in some details of this analysis.