Infra

Noun
A person who thinks they are cool, but is actually cooler than they consider themselves to be

Adjective
Thinks of themselves lower than they actually are, despite thinking highly of themselves

Example 1:
Person 1: See that person over there?
Person 2: Yeah he’s so infra

Example 2:
Person 1: I’m cool
Person 2: You’re not just cool, you’re an infra