Beefiness is defined as the quality of being strong and muscular, particularly in a person's physical appearance. In contrast, antonyms for beefiness would signify the exact opposite. These antonyms include thinness, slenderness, frailty, weakness, and emaciation. These words describe a lack of muscle mass, little to no bulk, and a frail or delicate constitution. Some other antonyms for beefiness could be delicacy, fragility, svelteness, lankiness, slightness, or spindliness. Essentially, these antonyms describe individuals who are slender and lacking in muscle mass. Beefiness, on the other hand, describes someone who has a muscular build and is generally larger and stronger-looking.