All 4 Uses of

coup

in

The Kite Runner

The end, the official end, would come first in April 1978 with the communist coup d'etat, and then in December 1979, when Russian tanks would roll into the very same streets where Hassan and I played, bringing the death of the Afghanistan I knew and marking the start of a still ongoing era of bloodletting.
p. 36.4

coup d'etat = the sudden overthrow of a government by use of limited force

In his absence, his cousin Daoud Khan had ended the king's forty-year reign with a bloodless coup.
p. 36.9 *

coup = sudden overthrow of a government by use of limited force

I remember Hassan and I crouching that next morning outside my father's study, as Baba and Rahim Khan sipped black tea and listened to breaking news of the coup on Radio Kabul.
p. 37.1

Blocking Hassan's way out of the alley were three boys, the same three from that day on the hill, the day after Daoud Khan's coup, when Hassan had saved us with his slingshot.
p. 71.3

Definitions:

(1) (coup as in: deposed in the coup)
the sudden overthrow of a government by use of limited force

This sense of coup is also called a coup d'état.
(2) (coup as in: a financial coup)
a brilliant and notable success

The term "coup de theatre" indicates a sensational moment in a theatrical stagecraft -- typically a surprise; or possibly a highly successful theatrical production.
(3) (coup de grace as in: delivered the coup de grace)
deathblow

(literally a sword strike that mercifully kills a wounded animal, or metaphorically as the last in a series of things that defeated an opponent, idea, business or other entity.)

The term coup de grace indicates a merciful death blow.
(4) (meaning too rare to warrant focus)