Cumbersome is an adjective, and it means hard to handle or deal with because of size, weight, or many parts; burdensome; unwieldy; clumsy. The idea is that something is so big, complicated,or badly designed that it is difficult to move or to use.
This adjective can be used for physical objects.For example, the sofa was so cumbersome that he decided not to take it with him to the new apartment.
We can also use this adjective for processes. A lot of processes in business are cumbersome. Of course, doing things with the government is often cumbersome because you have to complete a lot of forms, etc.
The worst may be when websites are cumbersome, because they should be quick and easy to use, exactly the opposite of cumbersome!