expression, godan verb (-u)
rest in the shade of a tree; take a rest under a tree
A somewhat literary or poetic set phrase for resting beneath a tree. The verb 憩う itself is relatively formal and less common in everyday speech; 休む is more typical for casual use.
旅人は大きな木陰で憩った。
The traveler rested in the shade of a large tree.
暑い日には、公園の木陰で
On a hot day, the best thing is to rest under a tree in the park.