On the sidelines is a phrase used to describe someone who is not actively involved in a situation or event. It can refer to someone who is watching from the sidelines, or someone who is not participating in an activity. The term can be broken down into two crossword solutions: IDLE (4 letters) and INACTIVE (8 letters). IDLE means to be INACTIVE or not doing anything, while INACTIVE means to be not engaged in any activity or movement. Therefore, someone on the sidelines is someone who is IDLE or INACTIVE, not participating in the event or situation.