Bastardise is a verb that means to corrupt or to make impure. There are several synonyms for this word, which include pervert, defile, taint, contaminate, degrade, adulterate, and spoil. The term pervert suggests twisting or distorting something from its original state, while defile implies a violation of something sacred. Taint suggests a subtle undermining of something's integrity, and contaminate indicates pollution or infection. Degrade suggests a lowering of status or quality, and adulterate implies mixing something with other substances. Finally, spoil suggests the ruining of something once considered valuable or desirable. All of these synonyms describe the act of bastardising something in various ways.