RTY - Rolled throughput yield
Typically used in six
sigma, it's the likelihood or probability,
in a percentage, that any given unit can go through an entire process
or procedure without receiving any defects. i.e.
Defect free processes.

For reference to chart above, see What
Are The Original Six Sigma Concepts And Theories and the 1.5 shift?
and Using
Defects Per Unit To Benchmark Different Products
Also see DFSS,
(design for six sigma), Waste-Free
Industrialized System, and Design
Margin - Statistical Tolerance.