Definitions of vex:

• verb:   subject to prolonged examination, discussion, or deliberation

  Example: "Vex the subject of the death penalty"

• verb:   cause annoyance in; disturb, especially by minor irritations
• verb:   be a mystery or bewildering to

  Example: "A vexing problem"

• verb:   change the arrangement or position of
• verb:   disturb the peace of mind of; afflict with mental agitation or distress