MultiKill

Multikills are actions that are done by the player which is defined as numerous kills within three seconds. It was implemented on the server on April 23, 2015, alongside the release of the Demolition kit.

There are two uses of multikill; one referring to both doublekills and triplekills, and multikills, while the specific definition is simply the multikill aspect of it.

Obtaining
To get any multikill, you must kill two or more opponents within three seconds. A double kill is awarded if you get two people, triple kill for three, and multiple for four or more. There is no known record for the most kills within a multikill.

Doublekills are very easy to get if performed on a popular server.

Addition
Multikills was included in the update of April 23rd / The Demolition Update, alongside the more famous Demolition kit implementation, and the teleportation smooth update, Server Restart fix, and the new Global Chat toggle feature.

Edits
On August 14, 2015, the two second interval was increased to three seconds, upping the previous timeframe by one second.

Trivia

 * Double-kills and triple-kills are not shown in public chat (only in the player's chat), but multi-kills are.
 * Since the August 14, 2015 edit, Multikills have became more common, as well as Doubles and Triples.