All 5 Uses

pious
in
Walden
(Edited)

It is the pious slave-breeder devoting the proceeds of every tenth slave to buy a Sunday's liberty for the rest.
Chpt 1 *

pious = self-righteous (believing oneself to be highly moral when it is not true)
Cato says that the profits of agriculture are particularly pious or just (maximeque pius quaestus), and according to Varro the old Romans "called the same earth Mother and Ceres, and thought that they who cultivated it led a pious and useful life, and that they alone were left of the race of King Saturn."
Chpt 7

pious = highly moral
Cato says that the profits of agriculture are particularly pious or just (maximeque pius quaestus), and according to Varro the old Romans "called the same earth Mother and Ceres, and thought that they who cultivated it led a pious and useful life, and that they alone were left of the race of King Saturn."
Chpt 7
The words which express our faith and piety are not definite;
Chpt 18 *

piety = religious or moral belief
His singleness of purpose and resolution, and his elevated piety, endowed him, without his knowledge, with perennial youth.
Chpt 18

piety = devotion or faithfulness to purpose

Definitions:

(1) (pious as in: a good, pious woman)
religious or highly moral
(2) (pious as in: a pious hypocrite)
self-righteous (acting as though one is, or believing one is highly moral when it is not true)
(3) (pious as in: cling to the pious hope)
(describing a hope or wish as) sincere, but highly unlikely
(4) (meaning too rare to warrant focus)
Much more rarely, piety can refer to devotion or faithfulness as Proust used it in the book, Swann's Way:

"...but when, as had befallen me, such an anguish possesses one's soul before Love has yet entered into one's life, then it must drift, awaiting Love's coming, vague and free, without precise attachment, at the disposal of one sentiment to-day, of another to-morrow, of filial piety or affection for a comrade."