Sentence:  The new propeller which was installed in 1982 was a <WSD>screwback</WSD> type with a diameter of 5,500 mm. and a mean pitch of 4,290 mm. 
Meaning of the word marked with <WSD> tags:  A type of propeller in which the blades are angled to produce a motion similar to threading a screw. Also, the angle of the blades on such a propeller.