A joint activity is an activity that involves two or more people working together to achieve a common goal. The term 'joint activity' can refer to any type of activity, from a business venture to a recreational activity. The crossword solution for the term 'joint activity' is FLEX, which stands for 'flexible collaboration.' Flexible collaboration is a type of joint activity that allows participants to work together in a flexible and adaptive manner, allowing them to adjust their approach as needed to achieve the desired outcome.