In plain words
Giving themselves over to immeasurable anxieties that end only with death, regarding enjoyment of desires as supreme and convinced that this alone is all,
Word for word
Given over to measureless anxiety that ends [only] in death, holding the enjoyment of desires supreme, convinced '[it is] this much',
चिन्तामपरिमेयां च प्रलयान्तामुपाश्रिताःकामोपभोगपरमा एतावदिति निश्चिताः
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
किञ्च —
चिन्ताम् अपरिमेयां च, न परिमातुं शक्यते यस्याः चिन्तायाः इयत्ता सा अपरिमेया, ताम् अपरिमेयाम् , प्रलयान्तां मरणान्ताम् उपाश्रिताः, सदा चिन्तापराः इत्यर्थः । कामोपभोगपरमाः, काम्यन्ते इति कामाः विषयाः शब्दादयः तदुपभोगपरमाः ‘अयमेव परमः पुरुषार्थः यः कामोपभोगः’ इत्येवं निश्चितात्मानः, एतावत् इति निश्चिताः ॥ ११ ॥
In plain words
There is more —
'Anxiety' -- and it's called 'immeasurable,' because there's no way to measure how much of it there is; that boundless anxiety, 'ending only with death' -- because it only stops when they die -- they cling to it, living in constant worry, always. 'Given over to enjoying their desires' -- 'desires' here means whatever is craved, the objects of the senses, things like sound and the rest; devoted entirely to enjoying those. Convinced, utterly, that 'this and only this -- the enjoyment of the senses -- is the highest goal a person can have'; certain that this much is all there is.
Close to the Sanskrit
And what more —
'Anxiety,' 'immeasurable' too -- that anxiety whose extent cannot be measured, that extent [is] immeasurable -- that immeasurable [anxiety], 'ending [only] at dissolution,' i.e. ending at death, they are absorbed in -- meaning, always given over to anxiety, that is the meaning. 'For whom sense-enjoyment is supreme' -- 'desires' are so called because they are desired, [meaning] sense-objects such as sound and so on; for whom the enjoyment of these is supreme; 'this alone is the highest human goal, namely the enjoyment of desires' -- thus of settled conviction; 'this much' -- thus certain [that this is all there is].