Mountain vs Massif

I always thought mountain and massif were interchangeable words but when doing some research I discovered that I was wrong. According to Webster a massif is "an elevated mass, usually mountainous with a number of peaks rising from it / a large portion of the earth's crust which has shifted as a block with out internal folding or faulting etc." In other words, it is a compact group of connected mountains that moves as one geological unit. Mt. Vinson is the tallest peak in the Vinson Massif which is part of the Ellsworth mountains of western Antarctica . At a height of 5,142m (16,860 ft.) it is the last of the seven summits which the Mallory family hopes to climb.