Sentence:  The departure was not unduly prolonged....Within the door Mrs. Spoker hastily imparted to Mrs. Love a few final sentiments...; a deep, guttural instigation to the horse; and the wheels of the waggonette crunched heavily away into <WSD>obscurity</WSD>. 
Meaning of the word marked with <WSD> tags:  The state of being unknown; a thing that is unknown.