Wordnet 3.0
VERB (2)
1. 
 defend oneself; 
2. 
 fight against or resist strongly; 
- Example: "The senator said he would oppose the bill"- Example: "Don't fight it!"[syn: fight, oppose, fight back, fight down, defend]
WordNet (r) 3.0 (2006):
fight back
    v 1: defend oneself
    2: fight against or resist strongly; "The senator said he would
       oppose the bill"; "Don't fight it!" [syn: fight, oppose,
       fight back, fight down, defend]