Wiktionary
vb. (context transitive idiomatic English) to gain (weight) quickly.
Usage examples of "pile on".
He had taken one of the white roses from the vase and was removing the petals, one by one, and arranging them in a pile on the table.
If, at times, in the Pitcairn narrative, blood flows over-freely, and horror seems to pile on horror, it is not because the authors would have it so: it was so, in Pitcairn history.
But if we have to, all the girls strip naked and pile on him in a giant scrum of bodies.
The six stones, grayish yellow with a metallic sheen, made a small, insignificant pile on the bed platform, yet one like them had made the difference between her acceptance and her rejection.
He leaves those in a pile on the smooth stone floor, and folds his few clean underclothes and good brown outfit, setting them on a shelf in the wardrobe.
I stood up, put the notebooks in a pile on the floor, and wheeled the bed table over.
I gave him an exaggerated nod, then waved him away from the rock pile on which I perched before turning back toward the slowly shrinking pile of rock.
But he forked over some toothpicks from a pile on his side of the tray.