Background: There is a need for standardized and universally accepted terminology to describe gluteal morphology and related pathologies. The growing popularity of permanent, nonabsorbable injectable fillers has introduced new challenges, including deformities, skin alterations, and systemic complications. However, the current vocabulary for gluteal deformities and filler-related complications remains insufficient, resulting in inconsistencies in diagnosis, treatment, and communication among health professionals. Objective: This chapter aims to develop consistent terminology for gluteal anatomy and deformities, focusing on complications caused by permanent injectable fillers. Introducing specific descriptors seeks to improve communication and enhance the diagnosis and management of filler-related conditions. Methods: Historical, cultural, and medical literature were reviewed to identify terms relevant to gluteal anatomy and deformities. Neutral, anatomically descriptive terms were proposed and designed to align with established medical terminology in other fields. The terms were constructed using Greek—and Latin-derived morphemes, adhering to medical word formation conventions. Results: The proposed nomenclature introduces a set of terms to describe various gluteal morphologies and deformities. “Megapygia” refers to prominently enlarged buttocks, while “hypopygia” denotes underdeveloped or deficient buttocks. “Hyperpygia” describes excessive anteroposterior projection, and “platypygia” characterizes flat or flattened contours when viewed from the same perspective. Skin-related deformities are addressed with terms such as dyschromatopygia, which indicates discoloration; atrophic gluteal rhytidosis, which describes prune-like skin; and allogeneic atrophodermia and allodermatomalacia, which refer to progressive skin thinning caused by fillers. Conditions resulting from filler migration, such as intergluteal caudal protrusion, commonly known as the “dirty diaper deformity,” are also included as Intergluteal caudal protrusion or Caudopygial hypertrophy. Additional terms like eurypygia, representing a broad gluteal area, stenopygia, and pygiostenia, which describe narrow buttocks, further expand the nomenclature. Iatrogenic allopygia is introduced to describe localized or generalized deformities caused by permanent fillers. A comprehensive table summarizes the terms, comparing lay language descriptions, medical explanations, and the proposed new terminology (Table 55.1). This table not only enhances clarity and consistency but also holds potential as a foundation for future expert consensus efforts. Additionally, it could serve as a valuable reference for future publications, supporting extended use and validation over time. Discussion: The proposed terminology provides descriptors for gluteal morphology and filler-induced deformities. Historical terms such as steatopygia and callipygia are adapted for modern medical use. The new terms can similarly be aligned with current medical literature while promoting respect for cultural and anatomical diversity. Conclusion: The presented lexicon provides a foundation for improved communication, understanding, and management of gluteal pathologies. Further refinement through expert consensus is recommended to ensure global applicability and widespread acceptance. This approach would help establish a universally recognized framework, enhancing clarity and collaboration across diverse clinical and academic settings.