The Collaborative International Dictionary of English v.0.48:

Jolly-boat \Jol"ly-boat`\ (j[o^]l"l[y^]*b[=o]t`), n. [A
   corruption of Dan. jolle yawl, or of D. jol yawl + E. boat.
   See Yawl the boat.] (Naut.)
   A boat of medium size belonging to a ship.
   [1913 Webster]