Wordnet 3.0
ADJECTIVE (1)
1. 
 not open to doubt; 
- Example: "she wanted to go that was for sure"; 
ADVERB (1)
1. 
 definitely or positively (`sure' is sometimes used informally for `surely'); 
- Example: "the results are surely encouraging"- Example: "she certainly is a hard worker"- Example: "it's going to be a good day for sure"- Example: "they are coming, for certain"- Example: "they thought he had been killed sure enough"- Example: "he'll win sure as shooting"- Example: "they sure smell good"- Example: "sure he'll come"[syn: surely, certainly, sure, for sure, for certain, sure enough, sure as shooting]
WordNet (r) 3.0 (2006):
for sure
    adv 1: definitely or positively (`sure' is sometimes used
           informally for `surely'); "the results are surely
           encouraging"; "she certainly is a hard worker"; "it's
           going to be a good day for sure"; "they are coming, for
           certain"; "they thought he had been killed sure enough";
           "he'll win sure as shooting"; "they sure smell good";
           "sure he'll come" [syn: surely, certainly, sure,
           for sure, for certain, sure enough, sure as
           shooting]
    adj 1: not open to doubt; "she wanted to go; that was for sure"