The Collaborative International Dictionary of English v.0.48:

Boarder \Board"er\, n.
   1. One who has food statedly at another's table, or meals and
      lodgings in his house, for pay, or compensation of any
      kind.
      [1913 Webster]

   2. (Naut.) One who boards a ship; one selected to board an
      enemy's ship. --Totten.
      [1913 Webster]

WordNet (r) 3.0 (2006):

boarder
    n 1: a tenant in someone's house [syn: lodger, boarder,
         roomer]
    2: someone who forces their way aboard ship; "stand by to repel
       boarders"
    3: a pupil who lives at school during term time

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "boarder":
   Brillat-Savarin, Lucullus, board-and-roomer, bon vivant, cannibal,
   carnivore, connoisseur of food, consumer, diner, diner-out, eater,
   eater-out, epicure, feeder, flesh-eater, fruitarian, gastronome,
   glutton, gourmand, gourmet, grain-eater, graminivore, granivore,
   herbivore, high liver, hungry mouth, lactovegetarian, lessee,
   lodger, luncher, man-eater, meat-eater, mouth, omnivore,
   omophagist, pantophagist, paying guest, phytophage, picnicker,
   plant-eater, predacean, renter, roomer, tenant, transient,
   transient guest, trencherman, underlessee, vegetarian