IPA: /ˈsɔːltləs/
KK: /sɔltləs/
Having no salt or lacking flavor; bland.
The soup was saltless, making it taste quite dull.
Saltless → It is formed from "salt" (from Old English *sealt*, meaning a mineral substance used for seasoning and preserving food) and "-less" (meaning without). The word "saltless" means without salt or lacking salt.
Think of something that is 'without' ('-less') the seasoning of 'salt' — that's why saltless means lacking salt.