Like whiskies! This could refer to both mixes of olive variety and mixes of virgen and other oils. In some cases it may also refer to a combination of oils from different plants.

"‘You’ll find that the blended oils are pretty bland compared to what are sometimes called ‘estate-bottled’ olive oils. " http://www.zaytoun.org/home/quality/tasting-olive-oil/

http://www.bbc.co.uk/food/recipes/mostof_oliveoil.shtml