An alternate plural form of avgas, though 'avgases' is more standard in aviation terminology.
A variant plural following an older or less common pattern for words ending in 's,' similar to how 'glass' can become 'glasses' or 'gas' becomes 'gases.' This shows English plurals can follow multiple patterns.
This word is a great example of how English has competing plural patterns—some people say 'avgasses' like 'gases,' while others say 'avgases,' and both are technically defensible depending on whether you treat 'avgas' as a whole unit or as a compound of 'gas.'
Complete word intelligence in one call. Free tier — 50 lookups/day.