An engagement ring with a large and flashy diamond; perceived to be expensive (and often is).

When worn by a girlfriend/fiancee the message communicated by the ring is "BTFO, I paid for this. She's mine... and she knows it."

Sometimes perceived as frivolous spending, the BTFO Ring may instead be a sign of:
(a) insecurity,
(b) distrust, or
(c) high-maintenance women.