"To bring down, lower, depress" (OED)--here an innuendo of the seminal emission. A III ii 77. (1) the brethren and sisters will abate the "stiffness of the flesh," i.e., they will depress or repress their stubborn gastronomic appetites; (2) the brethren and the sisters will abate the Stiffness of the flesh, the erected penis. I.e., they will deflate, lower, depress the erection by causing seminal emission through copulation. Quotation at Stiffness of the flesh.