All 5 Uses

bastion
in
Angels & Demons
(Auto-generated)

Langdon looked out at the towering stone bastions that loomed ahead-impenetrable fortifications surrounding the complex ... a strangely earthly defense for a spiritual world of secrets, power, and mystery.
Chpt 33-34 *

bastions = defensive fortifications
"If there is another way in," he said, "it's probably recessed in the rear bastion-more of an escape route than an entrance."†
Chpt 63-64
He sprinted toward the bastion, running on fumes, gazing upward at the citadel's circular core as it shot skyward to a gargantuan, sword-wielding angel.†
Chpt 105-106
Leaning out, he grabbed the top of the first bulwark, dragged himself onto the wall, and dropped onto the castle's lower bastion.†
Chpt 105-106
The tunnel inclined steeply as it left the Castle St. Angelo, proceeding upward into the underside of a stone bastion that looked like a Roman aqueduct.†
Chpt 111-112

Definitions:

(1) (bastion)
a strong defender or reliable example of something -- like a fortress or a person upholding a principle
(2) (meaning too rare to warrant focus)