WordNet sense 1 (a yawl used by a ship's sailors for general work):

jolly boat

WordNet sense 2 (full of or showing high-spirited merriment):

jocund, jovial, merry, mirthful

WordNet sense 3 (full of or characterized by joy):

joyous

WordNet sense 4 (be silly or tease one another):

banter, chaff, josh, kid

WordNet sense 5 (used as an intensifier (`jolly' is used informally in Britain)):

pretty