insure in WordNet English dictionary

1. be careful or certain to do something; make certain of something
   "He verified that the valves were closed"; "See that the curtains are closed"; "control the quality of the product"
   see  check  insure  see to it  ensure  control  ascertain  assure 
   
2. make certain of
   "This nest egg will ensure a nice retirement for us"; "Preparation will guarantee success!"
   guarantee  ensure  insure  assure  secure 
   
3. protect by insurance
   "The insurance won't cover this"
   cover  insure  underwrite 
   
4. take out insurance for
   insure