Refers to times when a person is more open to new ideas and learning, usually during childhood. Books can have a lasting impact on impressionable children.
Pro Tip 2/3
Not Just Youth
While often used for the young, it also applies to anyone who's open to influence, regardless of age. The new employee was impressionable and quickly adopted the office culture.
Pro Tip 3/3
Emotionally Charged
Can imply a vulnerability to emotional appeals or charismatic individuals. He was particularly impressionable to the motivational speaker's words.