The quick answer is yes.  The method you choose, however, depends on what type of attribute you are changing (measure or member name), how permanent you want the change to be and on your rights and privileges in the product.  The easiest way to change the column header of a measure is to right-click on the measure name in the Measure tab and select the Properties menu.

  

However, be aware that this method only works for you as the report builder, meaning it is not visible to other users. Check out the following link in the Help file to read about it: LINK.  If you want the change to be visible to everyone, you can leverage Overlays in the Admin Console (LINK) or leverage the Formulate module.

To do it in the Formulate module, select new Formula for the appropriate model and then choose the Measure object, if you want to rename a measure or the Member object if you want to rename a member.  In the example below, I grabbed the Measure object and dragged it onto the formula panel.  I selected the measure I wanted to rename and then saved it with the new name I wanted.

 This method is what you would call an Alias.  An alias is just an alternative name for an object.