Wordnet 3.0
ADVERB (2)
1. 
 with great speed or effort or intensity; 
- Example: "drove like crazy"- Example: "worked like hell to get the job done"- Example: "ran like sin for the storm cellar"- Example: "work like thunder"- Example: "fought like the devil"[syn: like hell, like mad, like crazy, like sin, like thunder, like the devil]
2.  used ironically to indicate the opposite of what is stated; 
- Example: "says he'll help me? Like hell he will!"
WordNet (r) 3.0 (2006):
like hell
    adv 1: with great speed or effort or intensity; "drove like
           crazy"; "worked like hell to get the job done"; "ran like
           sin for the storm cellar"; "work like thunder"; "fought
           like the devil" [syn: like hell, like mad, like
           crazy, like sin, like thunder, like the devil]
    2: used ironically to indicate the opposite of what is stated;
       "says he'll help me? Like hell he will!"