Undifferentiating is a word used to describe the lack of distinction or differentiation between two or more things. There are several synonyms for undifferentiating, including indistinguishable, homogenous, uniform, undistinguished, featureless, interchangeable, and identical. These words are often used to describe objects or people that are similar in appearance or function and lack unique characteristics. Undifferentiating can also be used to describe a lack of diversity or variation within a group or system. Synonyms for this context include monotonous, routine, unvaried, and unchanging. Overall, these synonyms emphasize the lack of individuality or uniqueness and the absence of variety or distinction.