pyramid scheme: a fraudulent scheme in which people are recruited to make payments to the person who recruited them while expecting to receive payments from the persons they recruit; when the number of new recruits fails to sustain the hierarchical payment structure the scheme collapses with most of the participants losing the money they put in
topsail: a sail (or either of a pair of sails) immediately above the lowermost sail of a mast and supported by a topmast