Undefined is absolutely clear in the spec.
Unspecified is whatever you want it to mean. I am also laughing, having never heard "unspecified" before.
Unspecified behaviour is defined in the glossary at the start of the spec and the term "unspecified" appears over a hundred times...
Unspecified behaviour is defined in the glossary at the start of the spec and the term "unspecified" appears over a hundred times...