What is it?
Becoming evidence of what you've seen and heard
Witness, as a spiritual discipline, is the intentional practice of letting your life become reliable evidence of what God has done through you. Your witness is expressed through the ways He has moved through scripture, through history, and through your life, so that others can experience it even before they ever hear it explained. It is not primarily a technique for starting spiritual conversations, an evangelism program, or a personality some people happen to have and others don't. Those things can absolutely serve our witness, but they are not witness in and of itself.
Dallas Willard framed it around formation rather than performance. Witness isn't a task added on top of discipleship, it's the natural residue of a life that is actually being conformed to Christ. Lesslie Newbigin put a communal spin to it, calling the local church itself "the hermeneutic of the gospel". Simply meaning people read a community's shared life long before they ever understand its doctrine. Put together, witness as a spiritual discipline is less like something you perform and more like something that becomes true of you and of your community, as you are formed by what you've actually seen and heard.
In the words of 1 John, that which we have seen and heard we proclaim. Witness is not a strategy, or a precise formula to rehearse, but rather a testimony to what has been encountered. Paul describes himself and the church as "the aroma of Christ" in 2 Corinthians 2:14-16. To some a fragrance of life, to others of death, but either way, it’s not something that is manufactured. It is the result of proximity. Everyone gives off some kind of evidence about what they actually love and trust (ever met a crossfitter?); the question witness asks is whether the aroma put out of your life is worth encountering. Witness, as a spiritual discipline, is to remind yourself of this truth and to actually express what God has already done, rather than trying to perform a version of him you haven't actually seen.

