One who indulges in alcohol/marijuana/drugs and the like only on occasion-- especially during social events. Tasters do not have as much experience as non-tasters with a given substance, since "tasting" is usually associated with gratifying oneself on a low-intensity level.
(During a toast at a formal fraternity event)
Nate: "Here's a special toast to all the tasters tonight! Let's live la vida loca!"
(During a standard college party)
Mitch: "Man, these tasters are really pissin' me off! They're wasting all our dank. Learn a little somethin' about courtesy and conservation before ya come strollin' through our pad, expecting a free pass, why don't ya?"