Definitions of trek:

• noun:   any long and difficult trip
• noun:   a journey by ox wagon (especially an organized migration by a group of settlers)
• verb:   make a long and difficult journey

  Example: "They trekked towards the North Pole with sleds and skis"

• verb:   journey on foot, especially in the mountains

  Example: "We spent the summer trekking in the foothills of the Himalayas"