Pitching in to refers to the act of helping or assisting in a certain task or project. However, there are several antonyms for this phrase, including not contributing, sitting on the sidelines, abstaining, not helping, or simply doing nothing. These opposing terms imply a lack of effort, willingness, or engagement in an activity where one is expected to contribute. By not pitching in to, one is not fulfilling his or her obligation or responsibility towards a team, organization or community. Therefore, it's important to encourage and inspire individuals to actively participate and contribute towards a common goal, rather than sitting on the sidelines and avoiding responsibility.