I agree with Willemina that what's meant here is probably 'buitenpot'.
My suggestion would be to translate the term as 'outer pot' or perhaps even 'ornamental pot' to distinguish it from the common red flowerpot.

This beautiful Amaryllis pot has an amazing feature, it's self watering! It's actually 2 pots in one (see below), an inner pot which holds the soil and bulb and an outer pot, which holds the water. The inner pot is porous, so the water in the outer pot slowly seeps into the inner pot, keeping the soil moist at all times.
http://www.amaryllis.com/prepotted/self_watering.htm

Winter care :- after the second flush of flowers is past (say May/June) cut back the old flowering stems to within 5cm of the base of the plant, remove the plant (still in the planter bag) from the outer pot and placed in a cool area, but where it will receive some sun. Water only enough to keep the mix barely damp and keep the slug pellets going. Your plant should then lie fairly dormant until early spring and, as new growth appears side dress with three month, high nitrogen fertiliser again, increase watering and place the planter bag back in the ornamental pot. During those winter months it is important to keep the plant as cool as possible as winter chilling is beneficial to delphiniums. Add another teaspoon of lime.
http://www.delphinium.co.nz/growingpots.htm