In grammar, a cumulative sentence is an independent clause followed by a series of subordinate constructions (phrases or clauses) that gather details about a person, place, event, or idea.  source

• "The unwieldy provision carts, draught horses, and heavily armed knights kept the advance down to nine miles a day, the huge horde moving in three parallel columns, cutting broad highways of litter and devastation through an already abandoned countryside, many of the adventurers now traveling on foot, having sold their horses for bread or having slaughtered them for meat."
  (John Gardner, Life and Times of Chaucer. Alfred A. Knopf, 1977)

• Here was this man Tom Guthrie in Holt standing at the back window in the kitchen of his house smoking cigarettes and looking out over the back lot where the sun was just coming up. (Kent Haruf, Plainsong)

• George was coming down in the telemark position, kneeling, one leg forward and bent, the other trailing, his sticks hanging like some insect’s thin legs, kicking up puffs of snow, and finally the whole kneeling, trailing figure coming around in a beautiful right curve, crouching, the legs shot forward and back, the body leaning out against the swing, the sticks accenting the curve like points of light all in a cloud of snow.

[An example of a complex cumulative sentence from Hemingway’s In Our Time --quoted in Miles, Bertonasco and Karns, Prose Style: A contemporary Guide (1991)