a piece of ground having specific characteristics or military potential
"Stunted" means "inferior in size or quality"--this adjective describes both the woodland and scrub ("dense vegetation consisting of stunted bushes"). Although the novel starts off during the rainy season, the stunted terrain emphasizes the shortage of water in Sudan. It also makes the walk more dangerous, because they don't have shade from the sun, places to hide from the rebels, or healthy fruits to eat.
The terrain changed from scrub to woodland; they walked among stands of stunted trees.
In Latin, "super" means "over" and "videre" means "to look"--these roots suggest that "survey" is a deeper inspection than "scan" (which comes from "scandere" and means "to climb"), but the example sentences from the novel use the verbs synonymously (see "scan" in this list).
Salva made it a habit to survey the whole group every morning and evening, searching for his family.
"Scan" is a contranym because it also has the antonymous meanings of "examine hastily" and "make a wide, sweeping search of"--because the group is large and ever-growing, Salva has to make his scan wide and sweeping. Because he does not have the time to sit and examine each face, his scan is hasty. But because he is looking for his family, he is intent on scanning each person's face as closely as possible.
One evening a few weeks after Salva had joined the group, he made his usual walk around the fireside, scanning every face in the hope of seeing a familiar one.
dignified and somber in manner or character and committed to keeping promises
"Somber" means "grave or even gloomy in character"--this adjective seems to be more fitting for the example sentence, but "dignified" could also fit because as an older man who has been in the army, Uncle would want to keep his face calm and steady to comfort his nephew.
His face became very solemn when Salva told him that he had not seen nor heard a single word of his family in all that time.
The given definition is for "despite" as a noun, but it is used as a preposition in the example sentence. With the similar sense of disregarding or ignoring, "despite" means "in spite of" but it does not always include contempt or dislike. In the case of Salva here, it connects his walking to courage, because he walks despite the cold terror that makes each step difficult.
Listening to Uncle, hurrying to stay close to him, Salva was able to make his feet move despite the cold terror throughout his whole body.