antiknock
adjective
an·ti·knock ˌan-tē-ˈnäk 
ˌan-tī-
variants or anti-knock
: serving or intended to prevent detonation in the combustion process of an internal-combustion engine
an antiknock agent
an anti-knock fuel additive
Word History
First Known Use
1921, in the meaning defined above
- unenlivened
- unennobled
- unenquiring
- unenriched
- unenrolled
- unenslaved
- unentailed
- unentangle
- unentangled
- unentered
- unenterprising
- unentertained
- unentertaining
- unentertainingly
- unenthralled
- unenthused
- unenthusiasm
- unenthusiastic
- unenthusiastically
- unentitled
- unentombed
- unentreated
- unenumerated
- unenviable
- unenvied