A cumulative or loose sentence is an independent clause followed by a series of subordinate constructions, such as phrases or clauses. The subordinate constructions gather details about a person, place, or thing. It is the opposite of a periodic sentence which has the main clause at the end.
Literary example: The Scarlet Letter
"She had dark and abundant hair, so glossy that it threw off the sunshine with a gleam, and a face which, besides being beautiful from regularity of feature and richness of complexion, had the impressiveness belonging to a marked brow and deep black eyes."(Hawthorne 7)