API UnitClassification

From WoWWiki

Returns the classification of the specified unit (e.g., "elite" or "worldboss").

local classification = UnitClassification(unit);

Parameters

Arguments

unit 

the unitId to query, e.g. "target"

Returns

classification 

String - the unit's classification: "worldboss", "rareelite", "elite", "rare", "normal" or "trivial"

Example

 if ( UnitClassification("target") == "worldboss" ) then
   -- If unit is a world boss show skull regardless of level
   TargetLevelText:Hide();
   TargetHighLevelTexture:Show();
  end

Result

If the target is a world boss, then the level isn't shown in the target frame, instead a special high level texture is shown.