WordPress custom theme
From Wiki @ Karl Jones dot com
A custom WordPress theme typically refers to a WordPress theme which you create yourself.
In the broadest sense, the WordPress themes which ship with WordPress as "custom themes", because someone created those themes. So too with all of the free themes available on the web. You might also think of WordPress child themes as custom, in the sense that you are customizing another scheme.
However, the term "custom" typically refers to themes you create yourself.