British slang, "bent" being slang for gay, and a "nine bob note" being a fictitious currency ("bob" is slang for shilling, or post-decimalization, a five pent coin).
Similar to US slang "queer as a three dollar bill".
That guy in the hot pants was bent as a nine bobnote!
noun:A sexual finishing move based out of the standing sixty-nine position where the male, after recieving full pleasurment from the inverted female, proceeds to pile drive her into the ground, rendering her dazed and or unconcious.
Suicide sixty-nine, the easy way to avoid the ackward after sex talk
Meaning ; I want It All, I'll take It All, I'll Take Everything.
Origin ; It's A Construction Term Used When Receiving A Delivery From A Cement Truck. Cement Trucks Used To Carry A Maximum Load Of Nine Yards Of Cement.