longboat

from WordNet (r) 3.0 (2006)

longboat
    n 1: the largest boat carried by a merchant sailing vessel

from The Collaborative International Dictionary of English v.0.48

Longboat \Long"boat`\, n. (Naut.)
   Formerly, the largest boat carried by a merchant vessel,
   corresponding to the launch of a naval vessel.
   [1913 Webster]