http://nl.pokerstrategy.com/glossary/
Polarising
A range is polarised if it is skewed either towards very strong hands or very weak hands. The expression "nuts or nothing" describes the polarisation of a range: If a player is trying to represent a full house by making an over-bet on the river for example, the player either has that full house or he doesn't have any showdown equity and is trying to take the pot with a bluff. Since he wouldn't make this move with a medium-strength hand, his range is referred to as polarised.
By polarising it, the range only contains two opposing types of hands (value hands and air), which makes it prone to exploitation. A player should therefore keep his range as wide as possible, allowing him to represent different hand strengths. This process is called merging your range (merged range).
Merging (merged range)
The term merging refers to the process of adjusting your range in a way that prevents it from appearing polarised. This means that the range of the player has to contain more than only two opposing hand strengths. By merging your range, you make it impossible for your opponents to put you on an accurate range in the long term. This in turn will inevitably force them into mistakes.
Example: K 
8 
2 
If a player only re-raises sets on this dry flop, his range is polarised and unbalanced. If he occasionally also re-raises air in addition to sets, his range remains polarised, but is balanced between very strong hands (sets) and air. If the player takes it one step further and also re-raises sets as well as air and top pair hands, his range is unpolarised and balanced (= merged range).
