(lying) flat on your back, looking up

We walked along the beach, past the rows of supine bodies soaking up the sun. 我们沿着海滩漫步，一路上到处都是一排排仰卧在海滩上晒太阳的人。

Compare: prone adjective (LYING DOWN)

If you are supine, you are weak and willing to accept the control of others.

The new director has introduced a series of changes against little opposition from the supine staff. 新任主管进行了一系列改革，并没有遭到软弱消极的员工多少反对。