Read this definition of discipleship from church:
Intentionally imitating Christ and reproducing increasing Christlikeness in others through caring relationships that practice accountability.
Various forms of discipleship: Family (parents and children), One-on-one/mentoring; Biblical counseling (issue-specific); Evangelism (from unbeliever to a believer); Sermons (being discipled by the Word); Sunday School (being discipled by the Word); Small group (more in-depth than sermon); Personal quiet times in the Word (being discipled by the Word)
There is nothing wrong with this definition, it’s one way to make concrete a nebulous concept. But I think discipleship can also happen unintentionally. You might be living out your life of faith without intentionally trying to disciple anyone, but when people see your life, they are motivated to do the same to be like Christ.
I am often discipled by people like that. Most of the time, they don’t even know they’ve helped me to grow in Christlikeness.