I. lie down phrasal verb ( see also ↑ lie )
1 . to put yourself in a position in which your body is flat on the floor or on a bed:
Just lie down on the bed.
2 . take something lying down informal to accept bad treatment without complaining:
I’m not going to take this lying down!
II. ˈlie down BrE AmE noun [singular] British English
a short rest, usually on a bed:
I’m going upstairs to have a lie down.