for certain

Also, for sure. Without doubt. For example, I can't tell for certain if this is the right color, or I know for sure that she has a new car. The first term dates from the early 1300s. The variant, dating from the late 1500s, is also used colloquially to express agreement or assert the truth of a statement, as in Mary is really bossy.--That's for sure, or Are you coming to the party?--For sure I am.

The adverb has one meaning:

Meaning #1: definitely or positively; (`sure' is used informally for `surely' as in"they sure smell good"
  Synonyms: surely, certainly, sure, for sure, sure enough, sure as shooting