He didn't want to go out on the weekend, just vegetating lazily on the sofa.

vegetating 是动词 vegetate 的现在分词形式。vegetate 来自名词 vegetable（蔬菜），引申为"像植物一样静止不动地生活"，指"懒散地躺着"或"无所事事地消磨时间"。