IPA: /ˈɔɪlpruːf/
KK: /ˈɔɪlpruf/
Able to resist or prevent the penetration of oil.
The oilproof jacket kept me dry during the rain and oil spills.
Comparative: more oilproof
Superlative: most oilproof
Oilproof → It is formed from "oil" (from Old English *oleo*, meaning a fatty liquid) and "proof" (from Old English *prūf*, meaning resistant or tested). The word "oilproof" means resistant to oil or able to withstand oil exposure.
Think of something that is 'resistant' ('proof') to 'oil' — that's why oilproof means it can withstand oil.