Sentence:  Over the rapidly <WSD>diminishing</WSD> outline of a jump seat piled high with luggage Herry 's black brushcut was just discernible , near , or enviably near that spot where - hidden - more delicately textured , most beautifully tinted hair must still be streaming back in cool , oh cool wind sweetly perfumed with sagebrush and yucca flowers and engine fumes . 
Meaning of the word marked with <WSD> tags:  becoming smaller or less or appearing to do so