The word “Gospel” is so familiar and frequently used that it is possible to lose sight of its genuine meaning, “good news.” This question is vital as we face a series of movements within our churches which seek to redefine the meaning of the Gospel. In each case we are being offered “another Gospel” (Gal 1:6). The Good News of Christ faces a threat on the order of that faced by the Galatian Christians.
The above paragraph is from the Westminster’s Seminary website. You can read the rest of it here.