Word wrap in gedit

Check in the status menu in the lower bottom corner of the Gedit window.

If you want to do it in a as per-file basis, you can use modelines https://help.gnome.org/users/gedit/stable/gedit-plugins-modelines.html.en.

For example have a comment in the first line of your text file. In this case, autowrap:nil will suppress text wrapping.

// -*-indent-tabs-mode:t;c-basic-offset:4;tab-width:4;autowrap:nil;-*-

Check Gedit preferences, or else you can use TextWrap

In the gedit Text Editor menu click Edit, and then click Preferences. A popup named gedit Preferences opens up. In the same popup on the first Tab named View, under the sub-heading Text Wrapping click the check box named Enable text wrapping, to toggle the text wrap feature on or off.

These steps have been tested for gedit 3.10.4 version running on Ubuntu 14.04 LTS.