The antonyms for the word "straightened up" are numerous and include words such as bend, curve, slouch, slump, hunch, stoop, crook, and arch. All of these terms imply a physical position or posture that is not straight, upright, or vertical. Instead, they suggest a degree of curvature or distortion that can be intentional or accidental. For example, bending over to pick something up is a deliberate act, while slouching in a chair may be a bad habit. Similarly, the terms "stoop" and "hunch" suggest a forced or uncomfortable position, while "curve" and "arch" imply a more graceful and natural curvature.