Someone who enjoys really hoppy beers, or drinks hoppy beers exclusively. Most likely this person is a beer-geek or craft-brew drinker.
Hops are what give beer the Citrusy, Piney, or sometimes what bring out the Herbal or Fruity flavors.
Man, that Stone Ruination IPA turned me into a true Hop-head.
One who habitually uses "hop" or opium. Also hop-habit: opium addiction.
"Lemme tell you 'bout Willie the Weeper,
Willie the Weeper, yeah, the chimney sweeper
He had the hop-habit and he had it bad
Lemme tell you 'bout a dream he had"
--old ragtime song about opium.