To heap (intransitive) is to mount up.
1838. The amount of money is a very high and heaping price.—Mr. Graham of North Carolina, House of Repr.: Cong. Globe, p. 470, App.
1873. Milton’s tracts are wearisome reading, and going through them is like a long sea-voyage whose monotony is more than compensated for the moment by a stripe of phosphorescence heaping before you in a drift of star-sown snow.—J. R. Lowell, ‘Among My Books,’ ii. 273. (N.E.D.)
