This is the 8871st most frequent Japanese word.
横たわっ
"横たわっ" means "lay down" or "lie down."
The term '横たわった' follows the verb '横たわる' which means 'to lie down', here used in the past tense to describe the position of the cat.
静かに横たわった猫が窓辺で日差しを浴びています。
The quietly lying cat is basking in sunlight at the window.
In this sentence, '横たわった' captures the action of lying down on the sofa due to fatigue in a past tense context.
疲れてソファに横たわった青年はすぐに眠りに落ちた。
The young man, who lay down tired on the sofa, soon fell asleep.
Here, '横たわった' describes the state of the rocks as being reclined or lying flat, used adjectivally to detail their positions.