Substitute' is a term used to describe someone or something that takes the place of another. The crossword solutions for this term include 'AGENT, ' 'RELIEF, ' 'DOUBLE, ' 'REPRESENTATIVE, ' 'SWITCH, ' 'LIEU, ' 'SWAP, ' 'TEMP, ' 'PROXY, ' 'SCRUB, ' 'sitin, ' 'ERSATZ, ' 'fillin, ' 'REPLACE, ' 'standin, ' 'altego, ' 'rotatein, ' 'SURROGATE, ' 'quidproquo, ' and 'BENCHWARMER.' An AGENT is someone who acts on behalf of another, while RELIEF is a form of assistance or aid. A DOUBLE is someone who looks like or acts like another person, while a REPRESENTATIVE is someone who speaks or acts on behalf of a group. Switching is the act of exchanging one thing for another, while LIEU is a French term meaning 'in place of.' Swapping is the act of exchanging one thing for another, while TEMP is short for temporary. A PROXY is someone who is authorized to act on behalf of another, while scrubbing is the act of cleaning something. Sitin is a form of protest in which people occupy a space, while ERSATZ is a German term meaning 'substitute.' Filling in is the act of taking the place of someone else, while replacing is the act of putting something new in the place of something old. Standing in is the act of taking the place of someone else, while an alter ego is a second self. Rotating in is the act of taking turns, while a SURROGATE is someone appointed to act on behalf of another. Quid pro quo is a Latin phrase meaning 'something for something, ' while a BENCHWARMER is someone who does not play in a game.