Sentence:  `` we the People of the United States , in order to form a more perfect Union , establish Justice , <WSD>insure</WSD> domestic Tranquility , provide for the common Defense , promote the general Welfare , and secure the Blessings of Liberty to ourselves and our Posterity , do ordain and establish this Constitution for the United States of America '' . 
Meaning of the word marked with <WSD> tags:  be careful or certain to do something; make certain of something