All 5 Uses of

defile
in
The Two Towers

With it he washed clean the stones that Wormtongue had defiled.†
Chpt 3.6 *

defiled = spoiled the beauty or purity of something

They had come to the desolation that lay before Mordor: the lasting monument to the dark labour of its slaves that should endure when all their purposes were made void; a land defiled, diseased beyond all healing — unless the Great Sea should enter in and wash it with oblivion.†
Chpt 4.2

The sun was up, walking among clouds and long flags of smoke, but even the sunlight was defiled.†
Chpt 4.2

But as these ranges approached one another, being indeed but parts of one great wall about the mournful plains of Lithlad and of Gorgoroth, and the bitter inland sea of Nurnen amidmost, they swung out long arms northward; and between these arms there was a deep defile.†
Chpt 4.3

As it bent sharply round the tower, it entered a narrow defile and passed not far below the hollow where he stood.†
Chpt 4.3

Definitions:

(1) (defile as in: it was defiled)
to spoil the beauty or purity of something
in various senses, including:
- pollute a pristine lake
- harm a reputation or good name
- damage or disrespect something sacred
- take a person's virginity in a disrespectful way
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

More rarely (but not uncommon in classic literature), defile can refer to a narrow valley or a march or passage through one.