Sentence:  Physical methods are sometimes used to reduce or eliminate fertility. Methods include physical <WSD>addling</WSD> and surgical sterilization. Meaning "loss of development," <WSD>addling</WSD> in the strictest sense is destruction of eggs by shaking. <WSD>Addling</WSD> has come to mean destroying eggs by any physical or chemical means – puncturing, freezing, or coating with vegetable oil. 
Meaning of the word marked with <WSD> tags:  The act of causing fertilised eggs to lose viability, by killing the developing embryo within through shaking, piercing, freezing or oiling, without breaking the shell or other outer layer.