The Only Use of

palpable
in
The Giver

Now, thinking about the feeling of fear as he pedaled home along the river path, he remembered that moment of palpable, stomach-sinking terror when the aircraft had streaked above.
p. 3.3

palpable = very apparent

Definitions:

(1) (palpable)
very apparent (so strong, it almost seems to take a material form that can be touched)

"Palpable" is frequently used to describe the intensity of an emotion shared between people who can see each other. The implication is that the emotion is so strong, it almost takes a material form that can be touched.
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

In medicine, "palpable" means that something such as a tumor can be detected by palpitation; i.e., a physician's touch.