OP_GREATERTHANOREQUAL performs a comparison similar to OP_LESSTHANOREQUAL but in the opposite direction. It checks if the second-to-top item is greater than or equal to the top item, pushing 1 (true) if so, and 0 (false) if not. This opcode is used in scripts needing a greater-than-or-equal-to comparison.
OP_Code Walkthrough
Returns 1 if item-1 is greater than or equal to item-2, 0 otherwise
Pop Top Item a
Pop Top Item b
Check if b is greater than or equal to a
Push Result