asaktabuddhihi sarvatra jitaatmaa vigatasprihaa |
naishkarmyasiddhim paramaam sanyaasenaadhigachhati || 49 ||

One whose mind is unattached from all aspects, who is self controlled, from whom desires have departed, attains the supreme state of freedom from action by sanyaasa.
asaktabuddhihi : one with unattached mind
sarvatra : from all aspects
jitaatmaa : who is self controlled
vigatasprihaa : from whom desires have departed
naishkarmyasiddhim : state of freedom from action
paramaam : supreme
sanyaasena : by sanyaasa
adhigachhati : attains
Most government jobs, and even private sector jobs, come with a built in end date known as the retirement date, which signifies the culmination of career-related actions. Similarly, when we perform our duty observing the tenets of karma yoga, we will eventually reach a point where we are ready to move onto the next stage in the spiritual journey known as sanyaasa. The aashrama system in Indian culture appoints sanyaasa as the last aashrama, the last stage in life, where the individual should renounce all their duties and life a lifestle of a sanyaasi, a monk.
Shri Krishna lists three characteristics of a person who has reached the stage of sanyaasa or monkhood. His intellect is asakta, it is unattached from all objects, people and situations. It no longer entertains the notions that this object is mine, or this person is my daughter and so on. He is able to do so because he is jitaatmaa, he has fully conquered his mind, it does not get agitated or excited by external stimuli. And even without external stimuli, it does not feel the need to act in the world, because it is devoid of sprihaa or desires.
Arjuna wanted to know the difference between tyaaga and sanyaasa at the beginning of this chapter. We can glean the primary difference from the teaching so far. The end goal of tyaaga or karma yoga is purity of mind, also known as sattva shuddhi. The end goal of sanyaasa is the attainment of brahman or the eternal essence. It is also known as naishkarmya siddhi, the state, the accomplishment where one becomes actionless, or all actions become totally spontaneous, like a river entering the ocean. There are no more internal cravings or external goals since one has completely transcended the effect of the three gunaas.