Is the Hunt a keyword that is a trigger?

Yes, Hunt is a keyword that functions as a triggered ability.

According to Rule 823.1, Hunt is explicitly defined as a "Triggered Ability keyword."

When a unit with Hunt conquers or holds a battlefield, the Hunt ability triggers, meaning it is placed on the chain and behaves like an activated ability (Rule 383.3). Because Hunt is functionally short for "When I Conquer or Hold, my controller gains X XP" (Rule 823.1.c.1), it follows all standard rules for triggered abilities.