To vegetate is to spend time doing almost nothing — not moving much, not thinking much, just sitting there while the hours go by. The picture behind it is a plant: alive, but not going anywhere, not making choices. It usually carries a mild complaint or a joke at your own expense: "I just vegetated in front of the TV all Sunday." Said about yourself it is light and self-mocking; said about someone else it can sting, because it suggests they are wasting their life. Sometimes it is used seriously and sadly about a person whose life has shrunk — someone stuck in a hospital bed or a dull job with nothing to occupy them. There is a related, much colder medical use, 'in a vegetative state', for a patient who is alive but not conscious; that one is not a joke, so be careful before using this word about anyone who is ill. In older, technical writing it can simply mean 'to grow like a plant', but you will rarely meet that.

（無所事事地）耍廢、癱著、發呆放空。台灣年輕人講「在家耍廢」「躺著爛」就是這個意思。注意這個字帶點負面或自嘲的味道，不是中性的「休息」。