The International Olive Council is the only intergovernmental organisation in the world to bring together olive oil and table olive stakeholders out of producers and consumers panels. This places is in a unique position as a forum for authoritative discussion on issues and interests of olive industry.
The International Olive Council (IOC) has developed a system for the objective organoleptic (tasting) assessment of olive oil in order to determine an oil’s quality and commercial trade value. This assessment method is based on panels of trained tasters recognizing the absence and/or presence of specific positive and negative (defective) attributes.
This system sits together with the chemical quality parameters defined by law like the EU regulations
With regards the chemical quality parameters and EU limit values please visit QUALITY PARAMETERS page. 

The extra-virgin olive oil has many organoleptic parameters. We can recognize the top 3:

Bitterness  
Olives are mighty bitter straight off the tree. So any fresh, high-quality olive oil must be bitter, which we perceive on the tongue. This flavor of olive oil is obtained from green olives or just darkened. It defines the basic flavor of quinine and caffeine conducted by the water inside the olives

Pungency
Stinging sensation in the throat which can force a cough. Pungency is that cough-inducing sting on the throat that's caused by the healthy phenolic compounds in fresh, high-quality olive oil.

Fruitiness
Refers to the aroma of fresh olive fruit, which is perceived through the nostrils and retro-nasally when the oil is in one’s mouth. The scent of extra virgin olive oil embraces various olfactory sensations such as almond, grass, green tomato, artichoke, etc.

Each of the above trait can have different  level of intensity, Light , Medium / Balanced, Intense
High intensity or ‘’Intense’’ doesn't always mean the best rank. It depends on how the 3 elements are combined together and it depends from the preference of each of us

We offer the following terms, with positives in green and negatives in red, to help guide you through your own tasting experiences.

GREEN:

Apple/Green Apple: indicative of certain olive varietals
Almond: nutty (fresh not oxidized)
Artichoke: green flavor
Astringent: puckering sensation in mouth created by tannins; often associated with bitter, robust oils
Banana: ripe and unripe banana fruit
Bitter: considered a positive attribute because it is indicative of fresh olive fruit
Buttery: creamy, smooth sensation on palate
Eucalyptus: aroma of specific olive varietals
Floral: perfume/aroma of flowers
Fresh: good aroma, fruity, not oxidixed
Fruity: refers to the aroma of fresh olive fruit, which is perceived through the nostrils and retro-nasally when the oil is in one’s mouth.
Grass: the aroma of fresh-cut (mowed) grass
Green/Greenly: aroma/flavor of unripe olives
Harmonious: balance among the oil’s characteristics with none overpowering the others
Hay/Straw: dried grass flavor
Herbaceous: unripe olive fruit reminiscent of fresh green herbs
Peppery: stinging sensation in the throat which can force a cough (see pungent)
Pungent: stinging sensation in the throat which can force a cough (see peppery)
Ripely: aroma/flavor of ripe olive fruit
Round/Rotund: a balanced, mouth-filling sensation of harmonious flavors
Spice: aroma/flavor of seasonings such as cinnamon, allspice (but not herbs or pepper)
Sweet: characteristic of mild oils
Tomato/Tomato Leaf: indicative of certain olive varietals
Tropical: indicative of ripe olive fruit with nuances of melon, mango, and coconut
Walnut/Walnut Shell: nutty (fresh not oxidized)

RED
Acetone: aroma of nail polish remover, associated with winey defect
Blue Cheese: aroma associated with muddy sediment defect
Bacon: smoky essence that may indicate oxidation
Burnt/Heated: caused by processing at too high a temperature
Cucumber: off flavor from prolonged storage, particularly in tin
Dirty: oils which have absorbed unpleasant odors and flavors of dirty waste water during milling
Dreggish: odor of warm lubricating oil caused by the poor execution of the decanting process
Fiscolo: refers to coconut fibers in mats occasionally used in older mills that may create a hemp-like flavor in oil
Flat/Bland: oils which have no positive or negative aroma or flavor characteristic of olive oil; may indicate presence of refined olive oil
Frozen/Wet Wood: sweet, dry, and untypical aroma/flavor derived from olives which have been exposed to freezing temperatures
Fusty: anaerobic fermentation that occurs when olives are stored in piles too long before milling
Greasy: flavor of diesel or gasoline caused by equipment problems
Grubby: flavor imparted to oil by olive fly damage to olives
Hay-wood: flavor of dried olives
Muddy Sediment: barnyard-like aroma caused by olives' prolonged contact with dirt before or after milling
Musty: moldy, humid flavor created by wet olives that have been stored too long before pressing
Metallic: oils that have had prolonged contact with reactive metal surfaces either during processing or storage
Rancid: the flavor of oxidation that occurs as the oil ages, often described as “stale nuts”
Rough: pasty, thick, greasy mouth feel
Sour Milk: aroma associated with muddy sediment defect
Stale Nuts: flavor of oxidized oils, rancidity
Winey: sour/vinegary flavor caused by aerobic fermentation of olives during processing (see vinegary)
Vinegary: sour/vinegary flavor caused by aerobic fermentation of olives during processing. (see winey)
Yeasty: aroma of bread dough; associated with winey defect