(idiomatic,colloquial) A ritual of two or more persons holding another person by the arms and legs, face up, while bumping them repeatedly on the floor. In modern times it is a lighthearted affair, generally performed only on a young person's birthday with the number of bumps corresponding to the person's age in years. Historically it was a hazing.
1975, Bess Kaplan, The empty chair, page 43:
I didn't tell the girls it was my birthday. First thing they always did was grab the poor victim's arms and legs and give her the royal bumps.