1. to do something to excess or to be overly enthusiastic
Don't go overboard with dinner, there are only two of us
When you 'go overboard' you go 'over the top', or do more than is necessary to complete the task or goal. It is an informal expression usually used in a humorous or negative context to express a waste of resources or energy. Related to the adjective 'overkill' and 'over the top'.