Final answer:
An extrovert is someone outgoing and energized by social interactions. John, being described as an extrovert, becomes more animated and friendly in crowds.
Step-by-step explanation:
The meaning of the word extrovert in the selection provided is someone who is outgoing and is energized by being around other people. An extrovert like John tends to become friendlier and more animated in social settings, drawing energy from being with crowds. This contrasts with an introvert, who might find social interactions draining and prefer solitary activities to recharge.