1. Of large size for its weight.
2. Of an awkwardly large size.

1. Hard to handle; inconvenient
2. Lacking in skill or dexterity; awkward

Difficult to manage or control.

Difficult to use or handle or manage because of size or weight or shape; SYN. unmanageable.

So as to be unmanageable.

Heavily, weightily, awkwardly, in a cumbersome manner