6:8  

ज्ञानविज्ञानतृप्तात्मा कूटस्थो विजितेन्द्रियः ।
युक्त इत्युच्यते योगी समलोष्टाश्मकाञ्चनः ॥६- ८॥

dnyaanawidnyaanatRRiptaatmaa kooTastho wijitendriyaH ।

yukta ityuchyate yogii samaloShTaashmakaaJNchanaH ॥६- ८॥

Source: Automatic ITRANS Transliteration

Content with abstract and concrete knowledge, the soul established in reality, having controlled the senses,

Integrated, is called "yogi," to whom are the same a clod, stone, gold.

Source: Milind S. Pandit

A yogi is called Self-realized who is satisfied with knowledge and understanding of the Self, who is equanimous, who has control over the (mind and) senses, and to whom a clod, a stone, and gold are the same.

Source: The Bhagavad-Gita: The Sacred Song

A person is said to be established in self-realization and is called a yogi [or mystic] when he is fully satisfied by virtue of acquired knowledge and realization. Such a person is situated in transcendence and is self-controlled. He sees everything--whether it be pebbles, stones or gold--as the same.

Source: Bhagavad Gita As It Is