Hornpipe is a nautically themed dance in the Dragon Quest series. It has a chance of making a single enemy dance, making them lose a turn.
ShipDance is a hybrid ability learned by advancing to rank 5 as a Mariner or Dancer immediately after completing the other. In the 3DS version, hybrid abilities no longer exist and Hornpipe is learned normally by advancing to rank 3 as a Sailor. Functionally, it works exactly the same as the skill Sultry Dance.
The hornpipe is a lively dance associated with sailors, typically performed by one person.