What is it called when a boat leans?

Answer 1

A list, the boat is listing.
A boat or ship sometimes lists to the right. That can be due to a number of reasons. Most likely too much cargo or ballast is on the starboard side of the ship. This is not a desirable condition. Ideally the ship should be level.

There are certain ships that when they operate certain kinds of engines they tend to list due to the torque of the propeller. One example is a 378' USCG Hamilton class Cutter. They often operate with one gas turbine running (because it's efficient). This causes the ship to list slightly to starboard.

It can also be because the vessel is consuming oil from the port bunker tanks, and the list will be corrected when they start consuming from the starboard bunker tanks.