IPA: /ɪmˈpjʊrɪst/
KK: /ɪmˈpjʊrɪst/
The highest degree of being unclean or contaminated, lacking purity.
The impurest water in the region was not safe to drink.
Comparative: impurer
Superlative: impurest
Impurest → It is formed from "in-" (meaning not) and "purus" (from Latin, meaning pure) and the superlative suffix "-est" (indicating the highest degree). The word "impurest" means the most not pure or the least pure.
Think of 'not' ('in-') and 'pure' ('purus') to remember that 'impurest' means the least pure.