This is derived from an Alien dialect from the future. It means "I know", "You don't say..." , and/or "Hmmm". It implies pondering something. Due to their harsh, technological based society their language is extremely cacophanous- using a lot of x's, c's, t's, and "k's".
"That was a extreme sunets tonight. All 3 suns were raibows..."
"Mahnaxt..."