Sentence:  A century ago , Newman saw that liberalism ( what we now might call secularism ) would gradually but definitely make its mark on English Protestantism , and that even high Anglicanism would someday no longer be a `` serviceable <WSD>breakwater</WSD> against doctrinal errors more fundamental than its own '' . 
Meaning of the word marked with <WSD> tags:  a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away