To volunteer to join in (with someone) to help out (with some task). Jim is always willing to pitch in and help with any housework that needs doing.We all pitched in and helped so that the house would be clean before Mom and Dad got home.The only way we'll get the project finished in time is if everyone pitches in and helps.
pitch in (and help)
in. to volunteer to help; to join in completing a task. If more people would pitch in and help, we could get this job done in no time at all.