armchair quarterback

plural armchair quarterbacks

1. UScolloquialidiomaticA person who watches sports on television, typically American football, who often verbally suggests plays or critiques the players and coaches.

   My dad is such an armchair quarterback; he recognizes every bad decision the coach makes as soon as the play is over and he knows whether or not it worked.

   1 more example

   To turn an armchair quarterback into a triple-threat man, just ask him to rake the leaves. He'll put up a terrific kick, pass the buck to his kids, and put up a long run.

   1959 Oct, “Notes on these changing times”, in Herbert L. Brown, Jr., editor, The Kiplinger Magazine: Changing Times, volume 13, number 10, Kiplinger Washington Editors, Inc., page 2

2. UScolloquialfigurativelyidiomaticA person who criticizes something in which they are not involved and lack expertise.