lying down

[Learning_English]

sprawl = to spread the arms and legs out carelessly and untidily while sitting or lying down:

Could you tell me what the "lying down" here means?
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Please let me know if I have made any mistakes in any of my sentences.

[Edison_Chen_e_c]

when you sleep in bed, you are lying down.
when you count the stars on the grass, you are lying down.