Look it up in Shuo Wen Chieh Tzu, an ancient etymological dictionary: "The dragon, the biggest of scaled animals, can be visible or invisible, thick or thin, short or long.
＜說文解字＞裡形容：「龍，鱗蟲之長，能幽能明，能細能巨，能短能長，春分而登天，秋分而潛淵。」