(1):

(v. t.) To make or set right; to correct from a wrong, erroneous, or false state; to amend; as, to rectify errors, mistakes, or abuses; to rectify the will, the judgment, opinions; to rectify disorders.

(2):

(v. t.) To refine or purify by repeated distillation or sublimation, by which the fine parts of a substance are separated from the grosser; as, to rectify spirit of wine.

(3):

(v. t.) To produce ( as factitious gin or brandy) by redistilling low wines or ardent spirits (whisky, rum, etc.), flavoring substances, etc., being added.