What is the definition of the tragedy of the commons?

Robert just found out that he is going to be unemployed within a month because his factory has invested in a robotic factory line and his skills are no longer needed. this means that robert is . the gdp within country d has begun to decline. as a result of decreased production, thomas lost his job designing cars. this means that thomas is . raquel has just been offered a job, but she has decided not to take it because she feels her skills merit better pay and a better position. this means that raquel is .