Coppice
Thicket
Heavy - or - dense
Balance
A stratus cloud.
In a way that's what dense means. If something is dense then a small volume of it will have lots of mass. Something that has lots of mass will be subject to considerable gravitational force, which is weight.
Density is determined by the amount of mass in a given volume. Something is considered dense if it has a high mass for a given volume, while it is considered not very dense if it has a low mass for a given volume. Materials with tightly packed particles are usually dense, while materials with loosely arranged particles are less dense.
A cloud is a dense visible mass of suspended water droplets or ice crystals in the atmosphere.
A synonym for the word "dense" is the word mass or the word volume
Warm air is less dense than cool air masses because of their density levels.
An object that is dense has a large amount of matter within a given volume, regardless of its mass. Density is a measure of how tightly packed the matter is in an object, not the overall weight. So, an object can be dense but not necessarily heavy for its size.
If the mass of a fixed volume of air increases, the density of the air becomes more dense. Density is defined as mass divided by volume, so as the mass increases while the volume remains constant, the density increases.
Usually a thunderstorm, but depending on the temperature a tornado can also form.