In the game of bridge, Ekren refers to a Norway. It can be seen as an example of the modern style of ultra aggressive preemptive bidding.
Responses to a 2♦ Ekren opening:
In responding to the 2NT relay the opener indicates whether (s)he holds a minimum or a maximum (because of their playing strength 5-5's are generally considered maximum), and - in case of a maximum - the distribution in the majors:
Variants of Ekren include the use of the 2♥ opening to indicate a weak hand with at least a 4-4 in the majors. This treatment has the advantage that the left hand opponent of the opener can hardly gamble on the fact that (s)he will get a second chance to bid.
Another variant that is popular in the Netherlands (where it is referred to as Tilburg Two) and Belgium is to accommodate the Ekren hands as a weak variant in the strong 2♣ opening. This leaves untouched the 2♦/♥/♠ openings which are commonly utilised in the Low countries as Multi 2 diamonds and Muiderberg (also known as Tartan or 'Jón og Símon') openings. Also, a 2♦ relay is now available to responder that can be used to ask for the longest (or better) of the two major suits.