1. Suppressing or eliminating engine knock in combustion engines
   - antiknock

See also: leaded

• signor
• signora
• signore
• signorina
• signory
• signpost
• Sigrid Undset
• Sigurd
• Sigyn
• Sihasapa
• sika
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• silage
• silane
• sild
• sildenafil
• sildenafil citrate
• silence
• silenced
• silencer
• silene