The word "outrivaled" means to surpass or exceed in a competitive context. The antonyms for this word are those that denote being less competitive or unsuccessful, such as underachieve, lag behind, fall short, and trail. These words suggest the idea of being left behind or not being able to keep up with others in a competitive environment. In contrast to "outrivaled," these antonyms convey a sense of defeat or failure, rather than success or achievement. Therefore, in a context of competition or comparison, it is important to recognize and understand these antonyms to communicate clearly and accurately.