as good as nonexistent; practically useless; too inadequate to count
Used when something nominally exists, but is so small, weak, incomplete, inconvenient, or useless that it does not serve its expected purpose. Most natural in the fixed-feeling phrase あってないようなもの.
The storage in this room is so small that it is practically useless.
説明書はあるけれど、内容が古くてあってないようなものだ。
There is a manual, but the information is outdated, so it is as good as nonexistent.
On busy days, break time is practically nonexistent.
A transparent expression from ある/有る 'to exist' plus ない/無い 'not exist'; the phrase conveys that something exists formally but not in any useful or meaningful sense.