Part of me wants to read Simon's character as a sort of medium, fully in tune with his own nature and the nature of the other boys. If I chose one word to describe his situation in the novel, I might go with "inward" or even "mystical" since Simon's experience was one of separation but, importantly, one of intuitive connection.
The single word that I would use to describe Simon's experience would be: VIRTUE
Definition: moral goodness, uprightness, a special type of goodness (According to Webster's Dictionary)
Simon exhibits his natural tendencies toward goodness and kindness. He helps to set up shelters for the other boys, he assists the younger boys to pick fruit from high branches.
Simon's actions are characterized by morality and an innate awareness that informs his actions. Simon does not need to be scolded or forced to help others. He also admires the natural beauty of the island on which they are stranded.
Only one word? "Intuitive" would have to be the one.
This chapter is "Huts on the Beach" and Jack and Ralph are discussing how no one really helps with the building of the huts and they are important since there is now the fear of the beast to worry about.
“They talk and scream. The littluns. Even some of the others. As if—” says Ralph to Jack.
“As if it wasn’t a good island.”interrupts Simon. Astonished at the interruption, they look up at Simon's serious face. "As if," said Simon, "the beastie, the beastie or snake-thing was real. Remember?"
Simon is the only one who has said that perhaps the island isn't a good one, bringing out the worst in humankind, which of course, is supported when he meets the Lord of the Flies in the forest later and immediately afterward murdered by his friends on the beach.
Later in Chapter 3, Simon goes alone into the woods with furtive, secretive movements. he pops between two bushes that are so close he leaves his sweat behind on them, and then looks back out to be sure he isn't followed.
Simon dropped the screen of leaves back into place. The slope of the bars of honey-colored sunlight decreased; they slid up the bushes, passed over the green candle-like buds, moved up toward the canopy, and darkness thickened under the trees. With the fading of the light the riotous colors died and the heat and urgency cooled away.
Simon's intuition about the lack of safety here is obvious.
This is your one word as Simon symbolizes Good, meets the Devil face to face, The Lord of the Flies, and realizes that he will be sacrificed. "Darkness poured out..." Meanwhile, just as Christ, he is betrayed by Ralph and Piggy later in this work
Look further at enotes for Simon!