There are numerous synonyms for the word "tiny arm." Some options include diminutive limb, small extremity, petite appendage, little limb, mini member, undersized appendage, dinky arm, and puny appendage. Other synonyms may include shrimpy limb, pint-sized extremity, slight member, and compact appendage. These synonyms are useful when describing a person or animal's lack of physical strength or small stature. They can be used in a range of contexts, including in medical settings, animal studies, and everyday language. Regardless of which synonym is used, they all convey the same meaning - a small, diminutive arm.