Wordnet 3.0
ADJECTIVE (1)
1. 
 suppressing or eliminating engine knock in combustion engines; 
- Example: "antiknock properties"- Example: "antiknock rating"[syn: antiknock, antiknocking]
WordNet (r) 3.0 (2006):
antiknocking
    adj 1: suppressing or eliminating engine knock in combustion
           engines; "antiknock properties"; "antiknock rating" [syn:
           antiknock, antiknocking]