It means "not very good." It means "just barely good enough."
"All we had for lunch was a little package of crackers. We sat down and ate our lunch, such as it was."
This means "We ate it at lunchtime. I'll call it lunch. It wasn't a normal lunch. It wasn't a good lunch."
A related phrase is "not worthy of the name." "We called our crackers 'lunch,' though they were not worthy of the name." They didn't deserve the name "lunch."