What is the meaning of touching the dragon's tail?

Go with the flow.

Dragon is the leader of scale insects. Wang Fu said that its shape has nine similarities: the head is like an ox, the horns are like a deer, the eyes are like a shrimp, the ears are like an elephant, the neck is like a snake, the belly is like a snake, the scales are like a fish, the claws are like a phoenix, and the palms are like a tiger. There are eighty-one scales on its back, with ninety-nine Yang numbers. Its sound is like a clanking copper plate. There is a beard beside the mouth, a bright pearl under the chin, and reverse scales under the throat. There is Boshan, also known as Chimu, above its head. A dragon cannot ascend to the sky without Chimu. Breathing into clouds can change both water and fire.