The Troubadour Dance emote is a reward from the quest One Piercing Note. The emote is the same as the dance done by the Troubadour dancers outside of the Citharede Abbey. Dancing with the dancers, which can be done before the emote is unlocked, will essentially make the player perform the emote.
It is quite often used as a taunt among players, given its provocative movements. It is particularly used in places such as the TzHaar Fight Pits, to taunt either those that have been killed, or those who are waiting for the next game.