A samsari is the one who does not know the atma. This is the essence of this verse.
कर्मेन्द्रियाणि संयम्य य आस्ते मनसा स्मरन् ।
इन्द्रियार्थान्विमूढात्मा मिथ्याचारः स उच्यते
karmendriyani samyamya ya aste manasa smaran
indriyarthan vimudhatma mithycacarah ca uchyate
yah – one who
karmendriyani – organs of action
samyamya – controlling
indriyarthan – sense objects
manasa – with the mind
smaran – remembering
aste – sits
sah – that one
vimudhatma – deluded
mityacarah – a person of false conduct
ucyate – is called
The one who , controlling the organs of action, sits with the mind remembering those sense objects is deluded and is called a person of false conduct.
We saw in the previous verse that if a person does naiskarmya i.e. does not do any action or remains action less, he still thinks I am the doer as by not doing anything and sitting quietly is also an action. Likewise, a person or a doer who gives up action by will, his or her life is also false. We saw that sarva-karma-sannyasi and karma sannyasi and the difference between different types of sannyasa. Mitya means false and acara means conduct (mithycacarah) and there means ‘false living’.
A person who does not know the atma is a samsara with all problems, inadequacies and so on. Just by giving up activities such a person cannot forget the sense objects unless his mind is also ready. The short summary of this verse is that just by taking up renunciation or withdrawing his senses or not doing any activity, his mind is not free. His raga dvesas are still in there but in dormant form and will erupt when the time comes or an opportunity presents. This was talked about in chapter 2 as well where we saw that you cannot control anger or desire and one fine day you have decided not to get angry. We have to learn how to slowly master this and get to the root of this. I.e. unfilled desires leading to dissatisfaction, then anger which leads to the destruction of the person.