Of the many adjectives used to describe the singular nature of North and South Korean relations, "normal" is one that rarely, if ever, crops up.

The complex, volatile and sometimes quite surreal geopolitics of the divided Korean peninsula are very far from ordinary, subject to wild mood swings between two countries that have technically been at war for the past 60 years.

But judging what is or is not normal in the inter-Korean context looks set to become an issue of significant diplomatic importance in the wake of an agreement the two sides reached this week that pulled them back from the brink of an armed conflict.

Under the terms, Seoul switched off loudspeakers blasting propaganda messages across the border after the North expressed regret over recent mine blasts that maimed two South Korean soldiers.

With the South pushing for a North Korean undertaking to avoid acts of provocation in the future, both sides settled for a formula stating the loudspeakers would remain unplugged "unless an abnormal case occurs".

"Abnormal" is a vague, abstract term to use in any diplomatic context, but using it in reference to aspects of North-South relations seems almost perversely meaningless.

- 'Nothing is really normal' -

"Nothing is really normal in this context. It would be abnormal if they had a normal relationship," said John Delury, a professor of history at Yonsei University in Seoul who specialises in China and North Korea.

The two Koreas can barely agree on anything, so there would seem little or no hope of a consensus on what kind of act may be considered to have crossed the line into abnormality as referenced by the agreement.

And South Korean officials clearly aren't offering to clarify, even from a unilateral perspective.

Appearing before a parliamentary committee on Wednesday, Defence Minister Han Min-Goo was questioned as to what the government would deem to be an abnormal case.

"Instead of defining any specific case as abnormal now, I think we would seek to apply the term when a certain situation arises," Han replied.

While the "abnormal" clause in the agreement may -- like the comments of ministers -- be wilfully imprecise, it doesn't necessarily follow that it is impractical or toothless.

Seoul was well aware that Pyongyang was never going to make any specific pledge to avoid provocation, but it wanted some term of reference that might be used as a stick down the line.

- Putting down a marker -

"This is what they had to do," Delury said. "Get something in there that puts a marker down. It may be vaguely worded, but it's something they can invoke," he added.

And while the "abnormal" label may be open to multiple definitions and interpretations, if invoked by the South in the future, at least one meaning will now be quite clear.

"Essentially it becomes a piece of shorthand," said Paik Hak-Soon, director of the Center for North Korean Studies at the Sejong Institute.

"South Korea can use it as a warning that it will switch the loudspeakers on again, without having to make that threat explicit. That's an effective tool," Paik said.

But a tool that will blunt quickly if over-used -- a real temptation given North Korea's proclivity for provocative behaviour.

"They will have to use it very sparingly," said Delury.

"Because there will be abnormalities -- we are swimming in abnormalities -- and if the South invokes it every time, it swiftly loses value," he added.

Other government officials have suggested it would be reserved for situations where lives have actually been taken or directly threatened.

The focus, in that case, would seem to be on border incidents, rather than grandstanding events like rocket launches or nuclear tests, which would be open to censure anyway as violations of UN Security Council resolutions.

- The uses of imprecision -

Choi Kang, vice president of the Asan Institute think-tank in Seoul, said definitions were beside the point.

"Inter-Korean relations are pretty abnormal anyway. We find it hard to agree, so imprecision or abstraction can actually be useful in overcoming differences," Choi said.

It is precisely because "abnormal" is such a subjective term, and so open to interpretation, that it was allowed to stand in the final agreement.

"It can be spun many ways, but between us, between the Koreas, I think there is a tacit understanding of what would be judged 'abnormal' and that's important," Choi said.