I expect a high alcohol beer, with a lot of complex flavors. One that the alcohol content will "sneak" up on you because it isn't very obvious in the taste.
Quoting from the Beer Judge Criteria:
Aroma: Complex with moderate to significant spiciness, moderate
fruity esters and low alcohol and hop aromas. Generous spicy, peppery,
sometimes clove-like phenols. Esters are often reminiscent of citrus
fruits such as oranges, but may sometimes have a slight banana
character. A low yet distinctive spicy, floral, sometimes perfumy hop
character is usually found. Alcohols are soft, spicy and low in
intensity. No hot alcohol or solventy aromas. The malt character is
light. No diacetyl.
Appearance: Deep yellow to deep gold in color. Good clarity.
Effervescent. Long-lasting, creamy, rocky, white head resulting in
characteristic “Belgian lace” on the glass as it fades.
Flavor: Marriage of spicy, fruity and alcohol flavors supported by a
soft malt character. Low to moderate phenols are peppery in character.
Esters are reminiscent of citrus fruit such as orange or sometimes
lemon. A low to moderate spicy hop character is usually found.
Alcohols are soft, spicy, often a bit sweet and low in intensity.
Bitterness is typically medium to high from a combination of hop
bitterness and yeast-produced phenolics. Substantial carbonation and
bitterness lends a dry finish with a moderately bitter aftertaste. No
Mouthfeel: Medium-light to medium body, although lighter than the
substantial gravity would suggest (thanks to sugar and high
carbonation). High alcohol content adds a pleasant creaminess but
little to no obvious warming sensation. No hot alcohol or solventy
character. Always effervescent. Never astringent.
Overall Impression: Strongly resembles a Strong Golden Ale but
slightly darker and somewhat fuller-bodied. Usually has a more rounded
malt flavor but should not be sweet.
Comments: High in alcohol but does not taste strongly of alcohol. The
best examples are sneaky, not obvious. High carbonation and
attenuation helps to bring out the many flavors and to increase the
perception of a dry finish. Most Trappist versions have at least 30
IBUs and are very dry. Traditionally bottle-conditioned (“refermented
in the bottle”).
History: Originally popularized by the Trappist monastery at
Ingredients: The light color and relatively light body for a beer of
this strength are the result of using Pilsner malt and up to 20% white
sugar. Noble hops or Styrian Goldings are commonly used. Belgian yeast
strains are used – those that produce fruity esters, spicy phenolics
and higher alcohols – often aided by slightly warmer fermentation
temperatures. Spice additions are generally not traditional, and if
used, should not be recognizable as such. Fairly soft water.