veg out

Reader's Digest 9月号のDeath by TVと題された記事からです。
If vegging out in front of a TV is your favorite daily hobby, you may be courting an early death - even if you're not overweight.
"veg" は植物を思い起こしますが、文脈からすると "vegging out" は「ごろごろ/だらだらしている」、「寝そべっている」と言うような意味の様ですがどうでしょう？　辞書で確認します。
・Wordnik: Informal To engage in relaxing or passive activities. Often used with out.; "After all, children have lots of education inside school and what they should have is time to come home and put their feet up in front of the TV and veg out and be entertained and also inspired," he says.
・Wiktionary: (colloquial) to vegetate; to engage in complete inactivity; to rest; After working hard all week, I decided to stay home and veg on Saturday.
"veg" は "vegetate" から出来たようです。 "vegetate" をCOEDで見ると：
1 live or spend a period of time in a dull, inactive, unchallenging way: if she left him alone, he'd sit in front of the television and vegetate
2 dated (of a plant or seed) grow; sprout[with object] cause plants to grow in or cover (a place)
"vegetate"/"veg" はvegetableから生まれたのは上の2.の意味からも分かりますね。