There are a few synonyms for the word "allomorphic" which could be used interchangeably depending on the context. One such word is "polymorphic" which means having various forms or shapes. Another synonym is "heteromorphic" which refers to the existence of different forms or types. "Dimorphic" is another synonym which describes the occurrence of two distinct forms or structures. Additionally, "alloplasmic" is another relevant synonym, indicating a change or variation in form or structure. All of these words describe a similar concept of variability or diversity within a single entity, and can be used to convey a range of different meanings depending on the context in which they are used.