The word "生龙活虎" is formed by combining two parallel phrases: "生龙" (live dragon) and "活虎" (active tiger), where "生" and "活" are adjectives meaning lively or vibrant, modifying the nouns "龙" (dragon) and "虎" (tiger) respectively. This juxtaposition creates a compound idiom that vividly portrays energetic and vigorous qualities through the imagery of two powerful animals, resulting in a meaning that conveys vitality and dynamism.