Sentence:  Perhaps the most familiar soft bearing alloys are the <WSD>babbitts</WSD>. These have been in use since the early 19th century when printer's type metal was utilized for machinery by casting it into holes drilled in iron housings. 
Meaning of the word marked with <WSD> tags:  A soft white alloy of variable composition (as a nine parts of tin to one of copper, or of fifty parts of tin to five of antimony and one of copper) used in bearings to diminish friction.