Fixidity is a noun that refers to the state of being rigid, inflexible or immovable. Synonyms for this word could include terms such as inelasticity, steadfastness, stiffness, unyieldingness and obstinacy. Each of these words offers a slightly different perspective on the same general traits of resilience and unchanging nature. Inelasticity implies a lack of flexibility or resilience, while steadfastness connotes loyalty and dedication. The term stiffness suggests a physical as well as a psychological rigidity, while unyieldingness and obstinacy imply a certain stubbornness or refusal to adapt. Each of these synonyms can help to convey a different aspect of the quality of fixidity.