What does John 4:17 mean?

The Samaritan woman had come to the well alone, during a hot and unpleasant time of day, in order to draw water. One would have expected her to come at a cooler time, and / or with other women. More than likely, given what Jesus reveals here, the other women in town wanted nothing to do with her.

In prior verses, Jesus began explaining the "living water" He could offer her. And yet, when this woman first asked for it, He instead asked for her husband. Jesus knew that she didn't understand the message yet, and wasn't ready for the gospel. Like seeds on hard soil, there needed to be a break before the truth could take root (Matthew 13:20–21).

So, Christ has two reasons to ask this question. First is to expose the woman to her own sin, to make her aware of her need. The second is to point out that, despite knowing about her sin, God still seeks people like her.

Her answer to Jesus is the shortest of her responses in the story. Even so, she is careful to phrase her answer in vague and unspecific terms. She simply denies having a husband. Jesus will fill in the rest of the details Himself.